Radio Control car telemetry
The devices like RN171 can transmit a video feed (given you have a controller powerful enough to feed video data to wifi module). It is possible with such modules.

But I would not advice to go with wifi
as:-

1) It will limit the range of your video feed depending on the wifi range

2) It becomes highly complex to send live feed from digital camera to a wifi module. Processor needs to be fast enough not only to receive the camera feed bu also to transmit it to wifi module.

Thus I would advice you go for wireless cameras as it takes a lot of complex work off you. It also increases your range way more than a normal wifi hotspot/ router.