i did the same thing but i used the deomotic home softgware for my htc desire.
and modified it to work with any rf controlled wall socket
its network controlled over the internet and both from my phone and from a random pc.
its programmed to turn on the garden lights at 9:30 and turn them off at 23:30
i use the arduino to read the rf codes from any rf 433 hz remote and transmit them back when needed.