I have been working on a miniature, low power wireless remote node based on the ATmega32U4 MCU (the same used in Leonardo Arduino). This is a Open Source Project, all design files and documentation is available here: http://harizanov.com/wiki/wiki-home/funky-sensor-v2/.
I wish to say that I am amateur, only started learning electronics on hobby level recently.
The highlights are:
- 2*2 cm in size, only few mm thick
- can be powered from a CR2032 coin cell
- 0.04mA @ 3V in sleep mode
- Programmed via the USB - just like Arduino Leonardo
- Has a RFM12B radio module for wireless communication with other sensor nodes or another node acting as a gateway (logging the data or forwarding it to the Internet)
- Option for on-board voltage step-up boost regulator
I build these by hand using hot air gun - a slow process, but the outcome is beautiful:
Comments are welcome