This is really cool. I've actually been working on something really similar.
Early last year, we built a a breadboard with a Teensy microcontroller (instead of an Arduino) to decode signals from off-the-shelf door and window sensors. At the time, we had to reverse engineer the protocol using a oscilloscope. :) The breadboard was tethered to an Android device, which was the brain of the system (and this let us do other cool stuff, like video, networking etc).
We're much further along now (with working prototype units). If you're interesting in this kind of thing, we ARE hiring. :) (http://elarm.com)
They cost significantly more (about as much as a decent PC) but I would not trust my property or life to anything less honestly. My Omni has been running without reboot for years and does security/fire/hvac/irrigation/lighting/garage door control and has an iPhone app for control.
I know it's "just" an arduino talking to another PC .. but after doing some drilling, soldering, glueing, screwing and general arduino-ing myself ( http://www.youtube.com/watch?v=N9Rj-NegE6E ) well done on actually getting something designed, done and "ready". If you inspire one person to pick up an arduino then that's compliment enough !
This isn't sending SMS over the radio network, it's hitting TelAPI over (presumably) the land line. A jammer would prevent the reception of the SMS at the site, which wouldn't harm this application because the whole point is that the owner is not present and needs an alarm.
It is, however, vulnerable to the outrageous latency problems (minutes, often) the unofficial messaging gateways have. I send my wife texts to her company blackberry because it's convenient, but ultimately had to duplicate them to her gmail address to ensure that she got them fast enough.
I have tried out. Well documented and you can get the breakout boards for $5 but I forget precisely where. Managed to get it working in UK on O2 pay as you go. Now in junk box :(
Watch out - you need a level shifter if you're using an Arduino or something as it has 3v3 operation. I used an old(er than me) HP lab PSU and a crudely hacked up set of BC548 switches as a level shifter. You need an antenna and a sim socket (my sim was cruely soldered onto 1/0.2 solid wire and plugged into the breakout board header).
If it doesn't have to be SMS only, there are various mass market "surf sticks" offered by providers on the cheap, marketed at laptop owners and the like. Many of them are just AT modems with serial ports tunneled through USB and then controlled by an application on the computer.
Adafruit, Sparkfun, Pololu, Seeed Studios, Leaf Labs
Also see Mouser, Digikey, Allied, et al
Radio Shack carries Arduino now, some do anyway.
My personal favorite is Adafruit because this one time, I whined to her about her webform not accepting my firstname.lastname@example.org and she fixed it and wrote me back in like five minutes, no joke. I do not know her personally and that was the first time I had ordered anything from her.
tl;dr Limor Fried is a bad ass, buy things from her store.
- What's the cheapest Arduino board that would work with this sensor? Wouldn't it be cheaper to get a Raspberry Pi?
- How much is the power supply?
- It would also be cool if there was a way to send SMS over the regular wireless, like with one of those cheap emergency cell phone plans. That would make it a really nice alarm, no need for the internet, and it can work off a PSU even if burglars shut down the power/internet.
He shows it on a teensy, which if you're decent with a soldering iron can be done for as little as $16 + shipping. power supply is usb so no extra cost there. not sure how well talking to a phone would do directly but worth checking into.
That's right on the money, but technically I'm using a nano. Any Arduino will work though. There are knockoff Arduinos out there too, but I like to give back to the Arduino organization by buying an official board.