CheerLights is a network of lights connected to Twitter! All of the lights and apps that are subscribed stay in sync with each other. We are all connected!
Just send a Tweet to @cheerlights with a color in it and all of the connected lights in the world will change to that color. Also, the apps for iPhone, Android, Chrome, and Twilio will also display, read, or announce that color too.
Wow - just think of a net connected drone - maybe a drone with Google Maps on board or pushing air quality stats to a database. That would be an interesting mash up. Also, it's nice to see a HackPGH'er on here.
The main hardware that others have used are Arduino, Netduino, and ioBridge. But, you can do more abstract things, like use CURL to send server uptime or embed a web page counter on your website that sends a Growl update or flicker an LED.
We built the API to be more like Twitter's API - so geolocation and status updates are built right in and gives raw sensor data more context. My house is completely connected and my things send me status updates. Dig in to the open source API and you can see the differences.