For a few years I have had visitors call me on a Google voice#. Tasker takes the notification, and translates it into a few different actions such as flashing the phone’s light in a strobe type way. Been using it as a sorta intelligent doorbell.
Via Sharptools, we can now use those notifications to operate our smart homes. Including opening the schlage or other locks. The key is scheduling in Tasker. Set up a profile such that an incoming call or text from 5551212 between 3pm and 6pm on a Wednesday opens the lock (and disables the alarm of course), and your guest doesn’t even need you to be present to let himself in the door. When his stay is over, deactivate or delete the Tasker profile.
Perhaps owners of bed/breakfast establishments could use this method. No need for keys if the guests have cellphones… which most travelers do nowadays.