I can't speak highly enough about What3Words. Mrs Prof and myself love the UK canal network and we either hire or borrow a narrowboat each year for a couple of weeks at a time. A couple of years ago, the main battery on a hired boat gave up the ghost while we were on a well known canal ring. We were in the middle of nowhere on the network and quite a few miles away from any human habitation. The postcode for the area concerned covered good few miles of the canal, something that's not unusual in the rural countryside. I had limited phone reception, but did manage to contact the marina.
By convention, narrowboat users describe their position to others by stating they are between any two given bridges - virtually all bridges on the network have a number. However, the two bridges concerned were some distance apart. Anyhow, I phoned the marina and tried to describe where we were to the less than helpful manager. His attitude left much to be desired so I asked him to install What3Words on his tablet. He thought I was winding him up initially. After some persuasion, I gave him the three words applicable to our location. He understood the meaning of the words eventually and told his engineer to install the app and head for the location.
The guy turned up two hours later with a new battery on a trolley. He had pulled it from where he was parked around half a mile away along the towpath and admitted he would have had a hell of a job to find us if it wasn't for the app.
The app is now used extensively by narrowboat users on the canal network and is recommended in the guidance manual on most hire boats.