Two Arduino Funnels synced over xbee. I have a hall sensor connected to one of them. But because it needs the 5v I have a dc to dc step up on the board. The sensor was drawing too much current and I couldn't get it to work, so I had to solder directly to the battery pins.
Because I need to read the sensor constantly, no delays are used in the blink code. It is all done with timers.
This is a proof of concept for work being done with Matt Cottam of Tellart