Here's a simple example of a way to use the ouimeaux library. The RPi's running a server that discovers a WeMo switch by name (specified on the command line), then essentially forwards switch input from the GPIO pin to the WeMo. With a power supply circuit to let it run off 110 AC and a nicer switch, you could mount this in the wall to control your WeMo a little quicker than pulling out your phone, for those cases when you're already in the room. Said my sister: "Congratulations, you've reinvented the light switch."
The switch circuit is the simplest possible; example circuitry and code can be found here.