jdev

Welcome to the forum!

Simplest would be to get a standard 110V to 5V regulated wall adapter, like this one:
http://www.sparkfun.com/products/8269

To only have a single network cable you could also use POE (power over ethernet) that can send 5V power through an unused twisted pair of wires within the network cable.

For the latter, you'll need both an injector (to insert 5V into the cable in one end) and an extractor (to get the 5V out on the Netduino side). Here's a complete set for that:
http://www.sparkfun.com/products/10759

To control lightning fixtures, you'll need a 110V relay that can be controlled by the Netduino. You'll also need some kind of motion sensor to detect when your child enters the room. Beware that working with 110V can be very dangerous and potentially lethal. I'd think twice before installing homemade 110V equipment in my house with respect to both my kids and insurance policies in case of a fire due to electrical malfunction.

Thank you for the reply, I have looked into the POE but then i would need to get a POE switch and a poe shield for each implementation, I guess i could just take apart one of those wall outlets... was just hoping to find some instructions or maybe a cheap breakout board that does it already.