I have been working on this for a little while now. While it isn't complicated, it seems to work rather effectively.

It is quite simply a trip wire that connects to a few IR LEDS so when a person trips the system, the beacon lights up. The beacon is only visible by night vision, no dull red glow, COMPLETELY invisible to the naked eye. It is designed for night time operations.

The idea came from a guy I know in Three Points and he was showing my team an area he works in. The area has a dozen routes of travel for smugglers to get from south to north, but unless they had a huge team, they could only cover two or three of the routes. So, I devised a cheap way to help cover those other routes. By placing a sensor that detects a person passing through and lighting up in the infrared spectrum, only those with night vision would see that the alarm was tripped. By shielding the LED's, you can limit the angle of view, reducing detection by those with night vision.

The deployment is simple:

• Choose a choke point along a likely advance of your target.
• Place beacon out of sight (designed for night time ops) but with a clear line of sight to your spotter.
• Bury initiation switch and connect trip wire.
• Place trip wire across choke point.
• Using night vision, wait for beacon to light up.

I have tested a few designs and right now I am able to get a few hundred feet between me with a shitty GEN 1 night vision scope and the beacon.

I need to talk with you guys in the field:
Is this is useful to you?
I would like to get it deployed with you guys if you have a need.

Designs:

The Mark 1 is simply a spring loaded switch that you can use a string based trip wire or a small stick trip beam. The beacon is 8 IR LEDs about an inch across in a circle to help with detection at longer ranges. The beacon needs to be within 15 feet of the tripwire.

UPDATE: I have successfully tested an IR proximity sensor and I am working to make it into a viable sensor.

I am working on a few other components to make it more useful:

pressure plate trigger
IR beam trigger
Sonar trigger
Ability for beacon to reset after a certain amount of time

If anyone is interested, let me know.