Everyday, I commit some code and all the necessary documentation for anyone who wants to reproduce it. Don't hesitate to contribute (for example, my english is not very good in the documentation), or ask for details.
I am now writing the code for the SPI communication between the Raspberry Pi and the ATtiny (the ATtiny is doing all the polling job, and only exchange with the RPi when something changes. I try to use nice programming technics for that (interruptions for the micro, async programming in Python for the Raspberry Pi)
I am also designing the 2nd part (upper part) of the wallet. I will soon post the design and update with pictures of the realizations.
My children should be able to use it/play with it in march, I hope.