Your garden variety motion detector uses IR, but these days, there are fancier technologies for achieving similar goals. If so desired, you can source yourself a microwave-based presence sensor ...
I recently picked up a couple of microwave motion sensor radar modules. You have seen (and perhaps tried) it before. This post is about the HFS-DC06 (DC5V/5.8GHz) Microwave Radar Sensor Switch Module!
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