Hi, Jack. Here's the tiny "arduino" I built a few years ago, a wildlife tracker. AVR Microcontroller and and accelerometer at the bottom end, discrete VHF transmitter in the middle (not popuated on this debug unit), and a break-away 6 pin header for programming at the top. Fully populated and with a battery could keep the weight under 2 grams for a two year battery life and 2-4 KM range. The worst part was dealing with the real-time clock installed on the back-side of the board. But with it the device can reliably wake up after months of hibernation and correctly choose to broadcast during night or day as need be - different species are tracked at different times of day.