@Andrew: I just want to briefly mention that the first support for using OpenSprinkler to control radio frequency (RF) wireless power socket has been added to the upcoming firmware 2.1.1. I’ve recently released the RFtoy gadget:
http://rayshobby.net/?p=9938
part of the purpose of this gadget is for users to easily obtain the wireless control code of these power sockets, then OpenSprinkler can simulate the remote to turn on / off these sockets.
Note that RF wireless sockets (typically 433MHz) are different from WiFi power sockets in that they are not WiFi based. On the plus side, RF sockets are much cheaper and widely available.