A:Answer If the AV out is 3 or more RCA jacks, and 2 of them are Red/White, then you can pick up the Audio there and Transmit it over BT. The video won't work with these simple boxes; if you want wireless Video and you have HDMI then just look up Wireless HDMI and you're in business. (Just remember some of those video transmitters get Hot while working; need ventilation.)
I've marked 2 Random examples below (Not "recommended", just Examples)