I'm part way through a SmartStat intelligent thermostat project at the moment.
It uses an arduino and 5 x 1wire temp sensors to read the temperature at 5 heights on my hot water cylinder and displays them on an LCD.
It also tells me how many showers can be expected based on the sensor readings (calibration achieved through our experience).
It also has the ability for the user to request a certain number of showers, it will then close a relay which simulates the cylinder stat closing and requesting hot water from the boiler
I'm planning to add a clock to it and also the ability to set a simple program (1 on and 1 off but could be expanded)
I'm not bothering with ethernet communication as i intend it to be a standalone device, but my experience with this project may help some of you.