Arduino Home Control. What started out as a simple way to open my garage door from my iPhone turned into what you see here.
As of this writing it can be used to open/close the garage door, check the status of the garage door, arm/disarm my security system, and send email alerts. The heart of this system is (obviously) an Arduino, but no ethernet shield was used. Arduino hacks. Scooterputer. I spend a fair amount of time zipping around town on my scooter, and thought it would be cool to add a voltage monitor to warn when the battery might need recharging.
Waiting until the electric starter no longer works is somehow lacking. So after an evening with an Arduino Duemilanove, I had a simple programmable voltage divider with 3 LEDs indicating battery low, good, and charging.