I don't think I have recommended an app before.
This is so unique and interesting that I can't resist.
A friend of mine traded houses with an acquaintance of his who lives in a vacation spot within a few hours driving time. The house exchange was made over a long weekend.
The person who came to stay in my friend's home got locked out about the middle of the weekend. There turned out to be no extra sets of keys available from neighbors or friends.
The solution turned out to be keyme. This is an app that lets you photograph your key and send it to someone else to have a copy made. The app even tells the recipient of the photograph where it can be manufactured at a locksmith nearby.
It worked perfectly and my friend did not have drive back from his weekend vacation to solve a fairly common problem.
Unfortunately keyme is currently only available for the Apple range of products. I hope it becomes available for Android soon.