This is the Prestige MV3 dual zone motion sensor.

Detects moving objects inside the vehicle using RF technology, rather than waiting for something to be struck or broken. That makes it the sensor for convertibles and for any vehicle parked with the roof or windows open, where there's nothing solid between a thief and your interior.

Dual zone means two levels of response: an outer zone for a warning when someone gets close, and an inner zone that triggers the full alarm when they reach in.

A shock sensor is still worth having alongside it. They cover different attacks: one detects impact, this detects intrusion.

See also the Directed 508D Invisibeam, which does the same job.