One project that I would love to do on the Pi is a programmable, web-interfaced, thermostat. Store-bought network-enabled thermostats tend to run in the hundreds of dollars and have limited options for custom programming. My current thermostat still uses mercury switches. It\'s been done with an Arduino here
but I think the Pi could do it much better. Just add a 1-wire temperature sensor (or several) and a USB wifi dongle (or get the B model and string Ethernet to it) and you can monitor the temperature and display it wirelessly. Those few GPIO pins that are planned for the Pi will be perfect for control functions: just hook up a few relays to them for the cool, fan, heat, and emergency heat (if you have a two stage heat pump) functions and you\'re golden.
The rest is just software. If I actually get around to doing this I\'ll probably implement it in Python, with a web interface to monitor the temperatures and program it. Depending on the number of temperature sensors I have, I could be as clever as I wanted to, for example monitoring the outside temperature, the output temperature of the vents (which tends to vary depending on heat pump efficiency and outside temperature), and even check the temperature for multiple rooms--if there\'s a major imbalance, turn on the fan only.
Is anybody else interested in this sort of thing? Anyone think I\'m underestimating how difficult this would be?