RF extenders consist of an IR sensor to RF transmitter module, and a RF receiver to IR transmitter(s) but are prone to RF interferences. IR to IR wired repeaters are more robust. The Hot Link Pro is a good entry level IR repeater and if you need more flexibility then check out the Niles system ([Link: nilesaudio.com]).

One advantage of an IR repeater (over the Harmony RF extender solution) is that it can be used with any IR remote including the original OEM remotes (in case your Harmony is in the shop for repair).