Well, we've built a prototype on a breadboard and added some code for the user interface. We slapped together an ESP8266 based NodeMCU with a small oled screen(I2C), a BMP 180 pressure sensor (I2C) and a gps breakout board (Serial), and for user control added a rotary encoder. Big reset button necessary in this stage of development..

Code is uploaded on Github, go take a look if you're interested.

Next steps are to add some functions to the code and work on the physical appearance of the thumb.