Hi I have managed to get tivo into a second room and controllable with the remote. (then send the signal to two other rooms with no loss in image or sound quality)
I have used the scart instead of hdmi. either way you'll need an infrared repeater ! i made one following this site ( if you have any electronics experience that is)
http://www.picprojects.org/projects/miniprojects.htm
scroll down to "IR Remote Control Repeater"
it cost me about a fiver to make, when i get 5 mins i will try and upload a picture of my system !
hope this helps
---------- Post added at 21:49 ---------- Previous post was at 21:44 ----------
just incase anyone does make the available circuit ,
The carrier frequency needs to be set to 40 Khz for the tivo remote to work ! ( jumper on the pcb is on )