Technically you don't need a TV at the ariel point for a video sender, just a Freeview box / Sky box whatever but this will only wirelessly send the picture for the channel that the box is currently displaying. Some senders will also transmit the IR signal from the box handeld remote to allow change of channel from the room with the TV.
But rojash is correct, there is no box that will "forward" the wall point to somewhere else in the house. To do this you would need to receive, encode, re-broadcast, decode, and retransmit the whole radio spectrum from 474 to 850 MHz which would cost a ridiculous amount of money even if it were legal which it isn't.