AirTag show speed

In order for the AirTag to be able to sense the vehicle's speed or direction, it would have to support GPS ... and it does not. Also, as Rudegar has pointed out, it is not designed for tracking. Instead, it was designed for the owner of the tag to locate a missing item that it was attached to.

no, it does not have an accelerometer and it's only means of communication is bluetooth so some 30meters if they have iphone with bluetooth enabled it can piggybag those to provide you with a location (their iphones location really) if not then it's dead in the water

it also informs their iphones that an unknown airtag is tracking them