I've installed close range wifi IP cameras (Microseven branded), maybe about a 15-20 m away and two walls appart. It's possible, but you will have to have a STRONG signal in order to avoid delays or getting a camera video a few seconds behind the other or the image to freeze occasionally...
As said before: an ubiquity might do the job, I'm about to do something like that, but I'm not going to use Ubiquity M2 Loco in direct connection to the camera, but to a DVR with two analog cameras and a Router. The DVR will transmit to a Desktop Computer where 2 or 3 DVRs will be viewed remotely with software integration.
(DVR--> Router <---> Ubiquity --> Wired Network)
I saw a good youtube video where he states (nearly at the end) that for real time video you NEED to use 802.11n Wireless, because it's optimized for ithttp://www.youtube.com/watch?v=7nTgQQbF9zo
It would be nice to see how it worked for you