This is pretty neat, but falls just short of awesome. What would really make it a killer app for me would be data collection — if it told you how much power the outlet is drawing so you could chart it and twiddle for maximum efficiency, etc. C'est possible?
I'm impressed with Wemo's set-up method - using the app to connect the device to the wifi network.
I'd love to be able to see a chart of power consumed and on & off times. Ideally I could download a csv file with all that data for each wemo device. This might be better achieved in a web interface with your wemo servers.
Very clever, and I like where it looks like you're going!