Common sense invention
Why don't the Lock Screens for smart phones have a space where the owner could provide his contact information (alternate landline telephone number, e-mail). As it is, if you have a password on your smart phone, then when someone finds it there's no obvious way to contact the rightful owner. At best, they drop it off with the local authorities and, with luck, it eventually gets returned.
But if the Enter Passcode screen had a spot for an alternate telephone number or e-mail address, then it would make things very easy for the finder to contact the owner.
Perhaps the alternate telephone number could even be an active button that would allow the call to be made from the found phone.
This improvement would allow lost phones to be returned within hours. Directly.