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Ask HN: Which smartwatch is the best in self-hacking/quantified self?
34 points by obsequiosity 17 days ago | hide | past | favorite | 17 comments
I want the smartwatch that gives the most control to the developer-end-user. It should expose all biosensor data to include EKG readouts so that a custom app can use it. In essence, I want a computer to take over part of my job to regulate myself - it should nudge me based on rules I set. E.g. if my blood oxygen saturation dips below a set amount while I've been sedentary for a certain time, I want a specific notification to breathe (as if I'm so intensely focused on a task that I forget). It's perhaps absurd, but you get the point - I should decide exactly how my watch functions in tandem with my unique physiology.


Garmin has always had about the best track record with data accessibility, by far.

Apple Watch is probably a very distant second -- especially now since they've really nerfed the health data exporting. Launch Health app, click on user photo, click "Export All Health Data", wait forever, have "fun" parsing it.

Fitbit's always been a jerk about holding the data ransom for paid membership tiers.

Looks like you can schedule HealthKit exports with this app https://apps.apple.com/us/app/health-auto-export-json-csv/id...

There's also this: https://apps.apple.com/hu/app/healthfit/id1202650514

It let's you schedule exports of some of your data to multiple sources. I use it to sync to Google Sheets, where I can easily build diagrams and data from it.

Do you have any specific recommendations from Garmin? They seem pretty good, but I have no idea which one to choose.

It just depends on your sports and desires. I use the classic 920XT, but I'd really love something like the 920XT (classic fav among triathletes) but with wrist-based HRM (in addition to chest strap compatibility).

The Garmin Instinct is pretty decent, but its going to depend on your list of desires.

Have a look at PineTime. No ECG though unfortunately.

If anyone is interested in blood pressure the closest I can find is the Richtek 1025. It’s an analog front end that can get ecg and ppg values which you can then use to get blood pressure values. I was looking and found an optical sensor that may work: biofy sfh 7072 biometric-sensor

Here’s some docs on the rt1025: https://www.richtek.com/Home/Design%20Support/Technical%20Do...

And a youtube video on their dev kit:


This really depends on what you want to measure and if you want medical grade equipment. While other commenters have mentioned Garmin, there's also Fitbit Sense which offers EDA, ECG, SPO2 and other biopotential -- Great app too.

In the medical/research sphere I would recommend Empatica, but it is quite expensive:

- https://www.empatica.com/en-gb/

Also, recording ECG on the wrist is not ideal. Other alternative placements are the biceps and of course the chest. There are specific sensing devices that measure what you're interested in that cover both locations, but inccur larger cost than Fitbit.

Just as an aside: your o2 saturation’s shouldn’t drop except in a disease state. Sitting still shouldn’t drop your sats. If you get a reading that does it’s likely due to artifactual reading.

Absolutely the Apple Watch. It’s got more sensors than anything else and a much more mature developer experience.

I worked on a research project for several years (ending around 2018) using smartwatches to record a variety of physiological measures like stress. We were always looking for an open platform to use, and tried a variety of Android Wear watches and the Apple watch, but found little with the features we wanted. Microsoft used to make a smartwatch that had open access to almost all the sensors via Bluetooth, but they stopped making them some years ago. So we designed our own. All the design info and firmware source is available here:


This let us build a custom operating system that could run multiple apps and include external sensors via Bluetooth plus a few internal sensors plus a link to a smartphone (and it's sensors). Near the end of the project I had a bunch of them (125 I think) made by an electronics assembly firm. If you want to build your own those files might be a starting point, but I'd also add the warning that many of the components, particularly the nRF51822 radio/MCU are likely no longer available in that exact version (Nordic changes their chip design often) which also means the firmware would need porting to the latest SDK. The touch interface chip is now obsolete. To get 125 built I had to pre-buy all the critical components we needed (some of them off eBay) and send them to the manufacturer. The e-ink LCD panels were hard to find also.

You might be interested in this:


That Arduino IDE generated firmware will run on a variety of cheap fitness trackers from China (the ones that use an nRF52832 radio/MCU). I haven't been active in this area for a few years so there may be new products available now. I see there are a number of self-built smartwatch projects on HackADay:


I'd also warn that getting reliable, accurate medical sensor data from a smartwatch or body worn medical sensor is not a solved problem. Unlike traditional medical sensors used next to a hospital bed a mobile sensor is subject to a lot of motion and environmental changes which messes with the readings. It's difficult to keep a sensor attached to one specific place on a human body. The more advanced sensors you'd like such as blood pressure are not available yet. Heart rate variability in Garmin's is usable, but wrist or body motion can throw it off. A chest strap such as a Polar H7 will give you a much better heart rate and HRV reading, but many people find them uncomfortable to wear. Blood oxygen readings can be fairly accurate when the person is not moving and the strap is tight, but will vary wildly once the person is motion. Be prepared to have to filter the data (e.g., throw out sensor data when the accelerometer indicates motion). Do a search for the new devices promising blood pressure (Samsung I think) or blood glucose monitoring (Apple). One of those might fit your needs when they become available. Beyond that have a look at medical web sites to see what hospitals are using (although those devices tend to require a prescription and are usually only sold to hospitals). You might find some leads here:


There are some research projects in this area too, here's one of the big ones:


led by Santosh Kumar:


Deborah Estrin has done a lot of excellent research on mobile health sensing as well:

https://en.wikipedia.org/wiki/Deborah_Estrin https://destrin.tech.cornell.edu/

Her Open mHealth project might be useful for making sense of the data you collect:


You might find some leads from Tanzeem Choudhury's work also:


though her work tends to use smartphones. Good luck!

> Do a search for the new devices promising blood pressure (Samsung I think) or blood glucose monitoring (Apple). One of those might fit your needs when they become available. Beyond that have a look at medical web sites to see what hospitals are using (although those devices tend to require a prescription and are usually only sold to hospitals).

This device is FDA approved to what you described (not blood glucose yet--but is technically capable): Biobeat Watch BB-613: https://www.bio-beat.com/copy-of-clinical-trials-and-researc...

It is Israeli technology and they do excel at things like photoplethysmography (PPG) and coulometry, from a historical standpoint.

But, the Empatica E4 is 100% capable of doing what you described above. You just have to use Lab Streaming Layer to interface with whatever you are programming in, such as Python. You basically reimplement prior research papers in your own code. However, it does not have an SpO2 sensor.

If anyone else can answer:

What is the best smartwatch that maintains privacy?

I have a Pebble Steel, but it will not sync with Gadget Bridge no matter what settings I try.

I use a Garmin Vivosmart 4 or a Xiaomi Mi Band (v4 or v5) and simply don't connect it to the smartphone. That gets you access to the data on your wrist, but no log of the data. Great privacy with no data collection. If you want data collection maybe you can find an app that doesn't upload to the cloud or write your own; some fitness tracking apps can talk to a variety of devices and don't use the cloud. The Gadget Bridge web site has a list of which devices are compatible with it:


They do list the Pebble Steel. I'd try the Mi Band 5. The Vivosmart 4 is somewhat unstable in my experience.

Any of these:

* Garmin (required to adhere to GDPR)

* Empatica E4 (required to adhere to GDPR) (for more advanced use)

* Microsoft Band 2 (open source API on Github)

* Suunto (required to adhere to GDPR)

Personally, the Garmin Fenix 6 or Garmin Enduro (if the new Enduro gets good reviews) are the ones I would recommend for general use.

Apple may do various appealing things, but they are not obligated to adhere to GDPR. The app creators for the Apple Watch are certainly not required to adhere to GDPR.

Ironically, the ones that adhere to strict privacy regulations tend to have more solid technology. These technologies have been utilized for impressive research in journal articles.

Also PineTime

There already is something that does what you are imagining, but in an even more discrete way: Spire Health Tags. You iron them on to your undergarment. Unfortunately, they are no longer selling them to people interested in biohacking or for non-healthcare reasons. But, they do sell for much cheaper than the retail price, which is ~$50/sensor, on ebay. But, here is the site for more info: https://www.spirehealth.com/. You could probably recreate them on your own super easily. The technology being utilized is certainly a Respiratory inductance plethysmography (RIP) sensor with bluetooth connection.

Otherwise, I would recommend starting off with a Garmin device. I personally use a Garmin Fenix 6X Pro, which I recommend. There is a new Garmin watch out, with updated sensors, called the Garmin Enduro, however, I do not know how it fares. It just came out within the past few days or so and there are very little reviews on it. I would not purchase a Garmin until you know if the Enduro is solid or not. It should be noted that the oxygen saturation (SpO2) on the Garmin Fenix 6 series can be questionable for some. I personally would not rely on it, but each update makes it better. [No wrist-based SpO2 sensor should be relied on for regular, non-strenuous activities at this point.] Regardless, Garmin derives your respiratory rate through something called the respiratory sinus arrhythmia. It is updated at a high frequency rate, to the point where you would get near-instantaneous alerts, if you set up your own app or configuration. You do not need an ECG sensor for this, and the photoplethysmography (PPG) sensor works great on the Garmin watches, for doing this. An ECG sensor really is not necessarily superior, and there are significant advantages to PPG sensors (like being able to determine the actual blood volume pulse of your capillaries).

Empatica E4 is the holy grail (which I have), but a Microsoft Band 2 (which you can get super cheap on ebay) does pretty much the exact same thing. There is a full working open source API for the Microsoft Band 2 on Github, which works excellently. For what the Empatica E4 is, it is very expensive. You also cannot use it without a direct connection to the internet. Here is a link to the Empatica E4: https://www.empatica.com/research/e4/. In terms of dealing with the internet problem, in my opinion, RADAR-BASE is the best way of dealing with that: https://radar-base.org/.

I also have a Respiban (a chest-worn device with peripheral sensors--but also monitors breathing), which I use in conjunction with the Empatica E4 and Garmin Fenix 6X Pro. But, it is better always to start off with the starter version of the Respiban, the Bitalino: https://bitalino.com/products/plugged-kit-dual-mode-ble-bt

Using my Respiban in conjunction with the Empatica E4, I used machine learning (via journal articles I referenced and re-implemented) to detect stress (both positive and negative) to a 95+% confidence interval. For both the Respiban and the Empatica E4, I utilize Lab Streaming Layer to interface with Machine Learning packages such as Keras.

But, for starting out, either the Garmin Fenix 6 or the Garmin Enduro will be the way to go.

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