Prices vary considerably.. Cheapest I saw was a 4 zone 'interior mount' for $26 which isn't bad. Putting the money into figuring out the control structure, modifying a power strip or adding sockets, etc.. Still fairly bulky, but it could work. Its got a nice interface too,
I am tinkering with a PIC 'system' to control my lights, heater, and fans, as well as monitor temperature (and use temp to regulate heater/fan on/off) and maybe pH. Will have a USB port so I can hook it up to my laptop to update the program, but no other controls except reset and power switches. Nothing new though, I know its been done before. Still waiting for my samples though...
Marty