I might suggest adding a list of cities you're live in. Right now I think you just have to intuit which cities work based on the address autocomplete.
Cute idea though! I'd be curious to see what your user-facing application looks like when you have an alarm set. Do you provide some sort of proof that the "alarm went off"? Package services usually take a photo of the door/porch as proof, might be a good idea in case anyone tries to dispute a charge for "not being woken up" heh.
Like another sibling comment mentioned, yeah, abuse potential is there. Could consider a snail-mail-letter-with-a-code verification method for addresses, though that's obviously rather slow.