Sometimes a Simple Solution is Best

A low-power, battery, or with solar cellular trespass monitoring solution.

The monofilament tripwire is located at knee-height. Contact with the tripwire will pull the short metal pin out releasing the magnet to fall inside the tube. A solid-state magnetic sensor embedded at the bottom of the tube changes binary state in the presence of sufficient magnetic flux density. This transition triggers a digital interrupt waking the micro-controller from a power-saving sleep-mode and sends an SMS signaling unexpected human presence.

In addition, measurement of temperature, humidity, battery strength, cellular signal strength, and trespass status are transmitted every hour for monitoring and threshold alerts.

Hall-Effect Switch