The crux right now is that it's pretty expensive to control things in the real world. One thing, fine. A couple things in close proximity, also ok. Many things,

The crux right now is that it's pretty expensive to control things in the real world. One thing, fine. A couple things in close proximity, also ok. Many things, distributed over the house? Expensive. Lets think of one device, a relay (or solidstate relay) that controls an outlet. You need: A radio, or a powerline networking unit ($10). Some sort of processor ($45 for a Pi w/ps and sd card). Some low level logic to connect to the relay ($.25), the relay ($2), and the power socket ($2). If you want to control two outlets at one place, you're only duplicating from the low level stuff to the power socket. That's another $5. If you want to do this at a location that's more than a usb cable away from site #1, you're in for another $50. The holy grail here is a wifi enabled power socket. All it needs is a small api: status and on/off. Bonus points if there's a current sensor. This could be done with the processor from Bunny's $12 phone and the power relay bits. But, it's got to be priced in the $10/socket range.