I already have it working on a breadboard:
I'm waiting for the boards to be released from customs :-/
The total code size is given at the end of the compilation thanks to the cmake-arduino tool, and it's size is ~886bytes. That was double checked with avr-size tool.
Here is an screenshot of the tool:
In the video publish above you can see the power consumption of the while system. About 2uA@3v, and near 1uA on stand by. (Look at the multimeter scale).
The source code, including a detailed explanation of how and why I did what I did is in the bitbucket repository.