I needed to find something that would hold my wire loom to the door skin, not flopping around and out of the way so the window doesn't rub it when it goes down. I went to Lowes and this was the only thing I found that didn't involve screws:
Unfortunately, they detached from the door when it got hot (summer in Florida). So I replaced the crappy foam tape with some decal tape that I've used alot and has never failed me.
It may be hard to see, but here's my wireloom coming from the keypad, down to the bottom of the door and up the other side. That's the connector on the bottom right.
Here's my box with the hole cut and some tape covering some pins to protect my wires. I used my first board since my new one didn't work out, but I was too impatient to try and troubleshoot it. I'll worry about it if I have any problems with this one (I haven't yet).
The back of the box, ready for mounting:
Here is an example of my splices into the door. Soldered together and double walled heat shrink with adhesive. This is the door lock sense wire, I believe.
Here's the box mounted. I can assure you that it's quite secure. I used just a tiny piece of the decal tape to hold it up temporarily while I was waiting for the other board, and it was harder than I expected to come off. Fully taped will definately hold it.
So it's been in my car for a while now, and I've had no problems from it at all. I'm very pleased with it. I don't used it all the time, most of the time my keys are more convenient, but there has been more than once that I was already outside and wanted something from my car and didn't have my keys on me. So it has already fulfilled its purpose. I'll sure be happy I did it if I ever lock my keys in my car.