This is a very simple instructable with the basic tools needed.
List of supplies:
Garage Door Remote
Normally Open Momentary Switch
Step 1: Disassembly
Under the buttons is a board with contact points for the buttons.
When you press the button, it creates a connection and the remote sends a signal. It's just like a momentary switch. What we're going to do is connect a lead to each half of this switch and then connect those leads to a switch that we can mount inside the car.
The 4th and 5th pictures show the seperate halves of the contact point in color. Red for one side, Black for the other.
Step 2: Wiring
One lead goes to the red portion of the switch and one lead goes to the black portion of the switch (colored in the second photo).
Be careful with the solder, you don't want any creating a short between the black and red part.
I suck at soldering.
Then we tape it up to help secure our connections.
Step 3: Reassembly
This step is optionally, I wanted to put everything back in it's case.
Step 4: Installation
The valet switch is powered, so I unplugged it from my security system. This switch also serves as the alarm status, I left that part plugged in.
I pulled the switch from the dash and spliced in the leads from the remote. There isn't a polarity concern, so it doesn't matter which wire is connected to which lead as long as they each get their own wire.
Step 5: Done
Looks exactly the same as when I started.
Here's a photo of another installation I did in my other car with a push button normally open momentary switch I got from Radio $hack.
If there was anything that didn't make sense or I left something out, please let me know. Hope you enjoyed.