I'm just laying out the schematic for a GPIO board that includes a 4x20LCD display interface, two mains relays, two opto-isolated mains power sensors, a real ti

I'm just laying out the schematic for a GPIO board that includes a 4x20LCD display interface, two mains relays, two opto-isolated mains power sensors, a real time clock chip and interface to some one-wire temp sensors. The Pi is going to be the master controller for my central heating system. There will be a Web interface and I hope to implement something with a service such as Google Latitude so I can have a 'back from holiday' mode where the system knows when I'm, say, back within 25 miles of the house and fires up the heating and water again. That's my fun project for when I have some spare time.