You'll have to pay close attention to the transmitter and receiver end of the equation. Most aren't going to transmit video with near-zero latency (lag), so if you are getting it for watching videos, the audio isn't going to sync with the video. Will be real annoying when the words don't match the lips.
I'm not sure what else is out there, but one to look for is aptx low latency. Both the transmitter and whatever is receiving the transmittion have to support the aptx low latency codec though.
And if you have to plug in the transmitter via optical cable, you'll need either a transmitter or receiver/headphones that can control volume as I'm not aware of TVs that will let you control the volume out over optical with the TV remote.