PIR motion sensor
Connecting this sensor you can detect if a human has moved in or out of the sensor range. They are small, inexpensive, low-power and easy to use. It is basically made of a pyroelectric sensor which can detect levels of infrared radiation. Everything emits some low level radiation and the hotter something is, the more radiation is emitted. If you connect OpenPlotter to internet you will be aware of what is happening in your boat when you are not there.
This item is available in our store