For what it's worth, two years ago I installed one of these $40 boxes from Cables To Go (related thread here from two years ago). I mounted the IR receiver for the repeater box in front of my TV next to its own IR receiver, so you always point the remotes to the same place, no matter what. It does have a bright blue LED that blinks whenever it receives an IR code, which could be helpful to you to debug the system, and then you might put some electrical tape over that part if your client doesn't like it.

Two years on, I'm still quite happy with this. A few months ago, I thought it was failing on me, and it turned out that the IR repeater was fine but my TiVo remote was flaking out. I bought a new one and everything's been groovy.