You might take a look at X10 camera's, not exactly what you are looking for in WiFi but I think meets all other criteria. www.x10.com
I have x10 camera's with motion detectors and a USB stick video recorder that the cam controller plugs into. This records only when the motion is tripped.
I use the X10 USB interface to the computer for more advanced control, but the computer is not required for them to operate, everything is wireless (except power), and I can, through the computer, manage, watch, and control the cams remotely, there is even an iPhone app for it.
I use mine in my home security system, 6 camera's on motion triggers and the video recorder. As it was for security I did only needed a picture good enough to "see" the person, so I am not sure of x10 cams will meet your quality requirements.