I have the Mule Driveway Alarm from Amazon now for almost three years. It triggers on metal objects only, no false alarms with the many Deer or the dogs. It triggers on objects as small as the neighbor kids ATV. The driveway was relocated slightly right after I put in the alarm but it was not necessary to move the alarm. It is not visible but if they try to drive around the other side they will hang up in a ditch.
I also have motion detector lights at the front of the garage, on a pole by the driveway, and in front and back of the shop.