Yeah, they did have these ambiance sensors, that go off when someone steps too close to the vehicle. Not sure about the motorhome, though, because of it's sheer size.
Most sensors can trigger a simple 12V
relay, which in turn can turn on anything you want. Like a digital doberman sound, or a clip from the Texas chainsaw massacre, or worst, one of the speeches of our governor.
Once I parked next to a Mustang at the mall, and the darn thing was trying to tell me that I was getting too close, it would call the police etc.etc.
Also, many alarms can be programmed to activate a pager. I am unsure of the pager's range, though.