Yes, an RF (radio frequency) remote works through walls and doors, but you can't use it unless the device you're controlling accepts a signal from that type of remote. Many of the satellite receivers come with an RF remote so you can have a TV located in a different room from the satellite receiver. Most TVs use IR (infra-red) remotes, so there has to be a line of sight between the remote and the TV.

Also, companies like Speakercraft sell IR repeater kits that allow you to use your remote to operate gear that is placed behind wood doors,

Any number of remotes have both IR and RF. Much cheaper to go the RF route than buying IR repeaters. Most tv's of fairly recent vintage have an RF wire attachment or have it built-in. IR's need line of sight, even with repeaters, the repeaters need to "see" each other to work properly. RF doesn't need any of that.

Greg

I used a set of these for a long time to control
a Dish Network box (IR Only) from another room.
It worked great for us.
I had the box feeding the TV in the room it was in
and another TV in the living room. Neither TV was
used very often so instead of paying for another box
we just set it up so one box could feed 2 televisions.
Just had to use these remote signal senders to transmit
the IR signal back to the set top box.

Pooh Bear

Here is a link that might be useful: RCA D940 Remote Control Signal Sender