Arduino-like Platform With Wireless and Video?
I think that your best bet would be a Linux based system. Something like Beagle Board.

Arduinos and their ilk tend to target low cost microcontrollers.

In order to stream video over a wireless connection, you're going to need a fast processor and a fast wireless link. I'd pick an ARM based system, running Linux with WiFi.

Here's an example of what can be done with a BeagleBoard:
http://mechomaniac.com/OpenCVBallTracking