I bought one for my parents' place, the probe is about 300yd through the woods from the house and it works just fine.
New 9v every 6 months.
Only issue is that with a wider driveway, you may not pick up some vehicles if they are far to the opposite side.
My parents have a wide gravel driveway,and if I hug the far ditch with my 350z, it won't go off.
Not an issue with paved or gated driveways.