Hagen is proposing using one of the IR outputs of the extender to drive an RF transmitter module similar to what I've shown using the Global Caché GC-100 at
[Link: mbx-usa.com].
The problem is that RF transmitter modules of the desired frequency may be quite difficult to find. 315, 418, 433.92, 868 and 915 MHz are easily found but transmitters for other frequencies are scarce. In Europe 433.92 & 868 MHz cover almost everything but North American RF equipment uses frequencies in the 300-1000 MHz range.
Hunter uses several different frequencies - see
[Link: mbx-usa.com]. One possibility is to cannibalize an OEM RF remote for the transmitter but that may be difficult and costly. I looked at one of their latest remotes and I would not attempt to cannibalize the RF section as it could not be done without destroying the remote. And, you still have the problem of capturing the RF codes from the OEM RF remote.