This would be great! Ideally, I'd love to see an integration with Liftmaster (I think they are the biggest) who uses the MyQ app. I'd love to see this work similarly to the RemoteLock / Schlage locks -- guest gets a unique code that starts and stops with their stay.
This integration exists today, although it is not well publicized. Jervis Systems (https://www.jervis.systems/) supports MyQ for both LiftMaster and Chamberlein. I have a house where i can't use a smart lock and their integration manages my Guest access through an app. They are about to roll out a web version very shortly - I'm suppose to get to Beta test in the next few days - so the guest won't have to download an app. They are also working on a virtual keypad for the MyQ integration so the guest can enter a pin on their phone and the garage will open/close.
See my post on the Lock Automation thread for more details: https://www.ownerrez.com/forums/requests/schlage-encode?page=4#72358