My wife and I used the Igloohome Smart Lock Box 3 for several years, and it worked very well as a key safe.
We used an 8-digit code. The code can be reset with the app, and the device has optional features such as that it can only be unlocked on certain set dates, etc.
However we realized it was not secure if one of us had access to the other’s unlocked phone, and could open the app.
Now we use disposable security tamper-evident money deposit bags.
The date of locking and the date of bag sealing is written on the bag, then the bag is sealed with the key inside, and a photo is taken of the sealed bag with its unique serial number. The date of bag sealing can be used to easily locate the photo later in a photo library, and check the serial number in the photo against the serial number of the sealed bag, ensuring the bag was not switched.
It is completely secure from unauthorized use, but the key remains immediately available for true unforeseeable emergencies. It is a wonderful solution for US $0.20 per bag.