I looked at the WeMo a couple of weeks ago and I think it's a great idea with a few minor wrinkles that need ironing out.
a) The ground prong is on the 'wrong' side - I could flip over every outlet and confuse the wife and everyone else, or install the plug-in modules upside-down.
2) Ipod only? Why not have the thing talk to android, PC and anything else that can talk to your network?
iii) variety - it looks like a choice of appliance module or appliance module plus plug-in motion sensor - They call it a 'family' of products, but it appears to be a single parent & only child family, with a distant cousin for the controller.
It's not all negative. WiFi integration is the way of to go. The web integration with the ability to use bits of the internet as triggers looks great without all the fiddling about with additional software. The design of the modules is modern when compared to clunky X10 and the smoother Insteon. Handles up to 1800 watts.
It's a mighty fine idea, but it needs polishing (or at least android or PC control) before I spend any money on trying it. I'd like to see a real MeMo integration device that could send/receive X10/Insteon commands; I'd buy one of those this afternoon and hide the credit card bill from the wife