Well I thought I would do my first writeup on doing a garage door opener button since I don't think I've seen a thread like this. I used to keep the garage door opener in my jacket pocket until I bought a new Taichi jacket and was a little too snug to keep the bulky opener in the pocket.
Very simple to do for under about $5 if you have the soldering tools and already have a garage door opener. Sorry for the crappy phone picks.
First off, you'll need the garage door opener, some wire (mine was 18 ga. I think?), a push button switch, some solder, and a soldering iron. You'll also probably want some flux (helps the solder flow) and a way to remove any solder errors (the mesh solder remover).
Once I popped the opener apart, I removed the buttons. The main opener button clearly closed a single position switch with four legs (A). I used the continuity function on a little digital tester to determine which legs were the closed legs when the button was pushed (B,C). These are the legs that need to be extended to the pushbutton switch.
The rest is easy. Just solder a pair of wires to legs B and C (this will obviously look slightly different on your garage door opener of choice) and solder those to the pushbutton switch. You'll want to use connectors of some sort so the opener isn't permanently attached to the switch. I also drilled two small holes (3/32"?) into the top of the opener case to thread the wires out. Its been a while since I did any fine soldering, so dont bash my crappy soldering job!
After that, I drilled a 1/2" hole into the little box on the right side of the frame (not sure what this box is for, if someone knows what it is or what its name is feel free to correct me). You can drop the opener right into the box, screw the pushbutton into the hole, and you're done! Easy and unobtrusive.