Heh, I used to use bluetooth GPS tracker with my nokia 770. It worked well since I could place the gps where it got the best signal. I could start a track, have it record it, and then check in with the n770 only when I needed to see a map. That way I made the most of my n770's battery life, but still got continuous tracking.
Beware that they take much longer to start since they don't know the GPS coords of the nearest cell tower, nor do they download the GPS almanac over the cell connection. They will however remember the almanac so you can leave it on for 30 minutes and not have to redownload it the next day.
I have a small Meshtastic device, not quite button-sized but still tiny. The chip on it supports aGPS, so I can upload the almanac and prime it with the approximate location. I'm very familiar with this process, I wrote a small utility for my cell phone back in ~2010 after I screwed up its factory image by installing Cyanogen.
Nice, I have a few mestastic widgets, but do want something small enough for a dog collar. That way my wife and I can carry a radio and keep one in the car so we have a good chance getting in range.
Sad that most of ham radio, which has similar APRS for tracking, doesn't do async or multi-hop.
Looks nice for some uses, but pretty big for a dog collar, almost 3" on a side. I've some long/thin dev boards that I could pair with an 18650 that should be closer to 1".
I'm planning to use a small LiPo battery with a JST connector. The whole footprint should be slightly larger than 3x4x1 cm. Still a bit too large for a pocket device, but perfect for a collar.
Sounds great, best I found so far is the RAK19007 (30x60mm), then add a GPS (RAK12500). It will be kind of long (60mm + case) but not too wide (30mm + 3d printed case).
Or the Mesh Node T114 Development Board V2 (23mm wide).
Beware that they take much longer to start since they don't know the GPS coords of the nearest cell tower, nor do they download the GPS almanac over the cell connection. They will however remember the almanac so you can leave it on for 30 minutes and not have to redownload it the next day.