Final solution: no SSL, inline JavaScript that changes the URL to ...?t=[unixtime]. If that time is recent, garage door opens.
All checked into svn (so I don't have to remember this all later), and tested... works great.
(As opposed to email, SMS, etc... I just have to hold one key and it works. Even if it takes 5-10 seconds, it's quicker than running inside, taking off shoes, etc...)
