If I read the first post correctly, he already has the Flash2Pass receiver mounted in his garage. So he can either buy the Flash2Pass transmitter for the bike, or he could buy the Harley receiver for the garage. I don't believe the two systems are compatible, but he can always contact the F2P folks and ask.
If it were me, I'd just use one of the remotes that came with the door opener. I wired one of mine to a simple pushbutton switch mounted to the inner fairing cap, with the remote located inside the fairing, and it totally outperforms the Harley system in terms of range and reliability. The Harley system seemed to have very short range and sometimes required multiple attempts before it finally opened the door. The remote and pushbutton setup I have now works first time every time and at a much greater distance from the garage door (like 200-300 feet versus 50 feet).
Jerry