Wireless, battery operated web cam for mobile robot
I don't believe that the Netduino has the processing power that you want to stream video over the network.  I believe that you could get any wifi webcam to work with the robot, though.  You would just need a little extra space in your power budget to account for the camera's additional power usage.

Depending on how soon you need the camera, I would just watch the winter sales on any of the big technology suppliers (Newegg, Tigerdirect, Amazon) for a deal on a wifi webcam that meets the specifications that you are looking for.

If you are looking to make your project entirely self-contained, then you may want to check out the CMUcam.  It provides a good vision sensor, without having to do much processing on your Netduino chip.  It can do most basic vision processing on-board, without the need for your chip to handle the processor intensive image processing.