when you accidentaly dial 911, you either say "oops, wrong number" or let police in for a quick check.
I think it's good they come check things out when such hangup happened.
I can see how such hangup can be the only thing a person in trouble can do.
It's quick and silent.
Ofcourse the police doesn't need to get all physical
Most of them are just frustrated people who think they can just go ahead and hurt people if they call them some nasty names or don't do exactly what they want.