When I worked at Cadillac as a tech, we used this:
https://straighttalkautomotive.com/O..._analyzer.html
It was a hand-held device with a long cord. The magnetic sensor could be placed at different places on the car to try and narrow down the vibration or rattle.
Caddy owners can be very picky about vibrations or rattles.
It was met with mixed results. Not to mention that when you are working flat-rate GM doesn't pay you for testing, only actual repairs.