So, I have a working remote gate sensor.
I purchased a cheap Neo Coolcam open/closed sensor off eBay for $17.50 free shipping.
My thought was to remove the reed switch and solder a connection block in its place.
As soon as I touched the connection to unsolder it the glass on the switch broke.
No big deal. I just used those wires to solder to the junction box.
I purchased a garage door open/closed reed switch for a wired alarm system from eBay for $12.17 free shipping. (No longer available, but here are a couple).
And 15 feet of micro flex conduit from a commercial supply store. It’s for running fiber optic cable.
Here is what it looks like.
(I will edit this with part number and cost).
But any kind of outdoor cable would work. I was worried about squirrels chewing on the cable is the reason I armored it.
I ran the cable through the same hole in the wall of the house used for my air conditioner and placed the modified open/close sensor inside the house.
The garage door switch mounts on one side of the gate and the magnet mounts on the other side. I used existing screw holes in the gate to mount the switch. The magnet had to be shimmed out a little but wasn’t difficult to find something to mount it. Home Depot sells some flat metal that is about 3ft long with holes above every inch in the plumbing department. Cost about $3.
Cut to length and screwed the magnet to it.
So for less than $40 I have a working gate monitor.
I’m going to create an instructable with better documentation and pictures.
I’ll post a link.