This project uses a YourDuino RoboRED (or Arduino UNO With Sensor Shield) to monitor the temperatures in a home. This is especially useful for people like me who live in rural Vermont and heat mostly with wood, with a small backup propane furnace. When I travel for several days it's important to be able to remotely monitor temperatures and make sure the furnace works and the house is not freezing!
UPDATE: This worked great for 10 days I was travelling! Turned the furnace on (up) on my phone in Montreal before driving home to Vermont. Checking the temperatures at home remotely gave us confidence everything was OK at home.