I'd also accept any suggestion about the microcontrollers, maybe a cheaper or more power efficient one?
You might want to use a real Arduino for your development work but unless you are using the serial monitor capabilities you don't need to deploy boards with on-board usb/serial programming hardware all around your house. Both Modern Device and Adafruit (and I'm sure some others) have boards without on-board programming capabilities that are roughly half the cost.
Don