If you’ve ever wished that you could get notification upon the delivery of your physical mail (just like you do with your email) then this hack is for you. Turn a wireless doorbell into a snail mail indicator.
Mime, a tinkerer from Denmark, wanted see if he had mail without going all the way to the ground floor of his apartment to check his mailbox.
He hacked apart a wireless doorbell and made a simple switch mechanism that would signal up to his apartment when the mail was delivered. Hit up the link below for more information including the schematics for his doorbell-to-inbox conversion.