I posted a few months back to see if anybody had done this. For 2012 BMW removed the standalone option for the homelink/universal garage door option, which is integrated into the rearview mirror.

Previously it was around $500, now it's part of the $3500 convenience package. I had no particular interest in the other components of the convenience package (nav, comfort access, cameras w/overhead view primarily), so I really didn't want to pay for the whole package.

A new homelink mirror was $850 from my local dealer, so I set out to buy a used one on eBay. It looks like all the homelink mirrors for all the BMWs made in the past 6-8 years or so are all the same, the only significant difference being a big or small clown nose. I found one with a small clown nose on eBay for $300 + $20 shipping. I think it was taken off an older 7-series, circa 2008 if I recall correctly.

I didn't feel like messing with installation, mainly because I was worried about some of the pre-wiring being tucked up by the sunroor and having to fish it out. So I paid the dealer $55 for installation. Just got the homelink programmed today and I'm happy to report that everything works just fine. FYI if it helps anybody, holding the remote 1-3" away for programming as described in the instructions didn't work. Actually touching the remote to the mirror did the trick though. So I ended up spending close to what BMW used to charge for the option, but managed to save myself about $3000 in unwanted options. Hope this helps somebody else in the same boat I was in.