You might want to take a look at the PowerMid
. It's a system comprising two units, one that receives IR and transmits it as RF, and another that receives the RF and transmits it out as IR again. It's a IR repeater system that uses RF, so you can relay IR from any normal remote (including most IR keyboards) to another room.
I haven't found an RF keyboard besides the Logitech, and a range of six feet isn't very useful for home theater applications. I'd have to put the RF receiver under the middle of the sofa to be sure it'd work for anyone sitting on it.