Wish we had a native Ning video chat. Their competition has had one for years.
Don't know anyone who's using a third party video chat app, but you can always try Tokbox found in the Ning App Directory. I don't know if it's limited to just your members, but it should be.
This would be easy to code if you have a little budget to back up your social warhorse.
Look into SIP technology. The player can be rendered via browser. People could actually call to connect into the chat (obviously audio only). Lot of cool options without the hassles of VOIP host exclusiveness.
I don't mess with SIP to much. But message me, I can refer you to a guy in Argentina, hes a fanatic of SIP tech. Speaks great english, runs a business server on the side, and most importantly, hes down to show you the demo, but no "time trial" test drives.
The Skysa chatroom has video capabilities, and integrates with your member database.