The Payphone Project
github.com
github.com
If you can get your hands on (or build yourself) a red box [1], you could even hack your own hack.
I vividly remember the last time I used a payphone like this calling my then girlfriend (became fiance, became wife) outside a 7-11 in rural virginia before the turn of the century. Nostalgia by the bucketful.
I suspect the Payphone Project's mailbox locator was one of the first crowdsourcing web applications and predated the USPS effort.
He never fails to brighten the day of whomever greets him at the door at our house :)