I'd propose the
TI Beagle Bone and this Wifi device
rovingnetworks.com RN_121.
The TI Beagle Bone boots in under three seconds. It is a full Linux system inside. The thing I like is the Node.js using the Cloud9 IDE. But you could program in the language of your choice. $90.
The RN 121 is a WiFi device that has digital inputs and outputs, analog inputs and a UART for data streams. $40
The Bone isn't going to do onboard video processing, on the other hand there are lots of better add in hardware that would be able to do that. Nice thing about the Bone someone smart could put a image processor on a "cape".
If you want a few more CPU cycles then the Beagle Board is a better choice at about $180