...to within a 3m x 3m square.

The App is called "what3words", and here's a location from it.

So, if somebody asks, "Where on earth are you?" then instead of the rather literary reply:
"I'm at the north-west corner of Market and Castlereagh Streets Sydney", you could instead say:
"dining.mugs.flat"...

It rather puts paid to the direction "Ah, you can get lost!", though it might engender some
other choice response from the uninitiated

It works off-line as well.