NUT Find tracker can be purchased on Amazon or ebay for about $5-15 each depends on where your purchase and which version you got. They are all based on nRF51xxx RF IC.
This show and tell will present 4 versions I can find on the market. I will teardown each one, compare and summarize pros and cons for each version, how to program it, and demonstrate GPIOs if you want to re-purpose it.
NutMini Smart Tracker
This is the thinnest device of the 4, physical size is 36.1(W)*24.5(H)*5.05(D)mm. It's the only one use CR2016 coin battery, which is half the thickness compare to CR2032 and less than half capacity. So theoretically it would have much less battery life.
It provides 7 GPIOs on PCB, as well as VBatt/GND/SWDIO/SWDCLK for SWD debugger connection.
Some internal pictures:
To be continued...