This would be fairly easy to make. I haven't built a remote extender, but I have built several IR tranmitters and receivers. Basically you just have to combine the two to make an IR transceiver. The parts list would be small, IR receiver, amplifier, IR transmitter (IR diode), and supporting caps and resistors. As long as the receiver module doesn't include the demodulation then the signal should be able to pass through the transceiver. If you get a good IR receiver then you won't have to worry about sunlight because most of them are shielded from other light sources, and only pick up the IR spectrum. They also usually include a bandpass filter (fc = 40kHz) so you get the signal being sent from the remote and not the noise from other light sources. This sounds like a fun mini project. I think I have most of the parts already, so I'll build it and let you know how it works out.
(Message edited by wakeprodigy on October 03, 2005)