What3Words is a free app that you can download to your tablet or smartphone.  It assigns a 3-word code to every 3 metre square on the surface of the Earth.  On most devices it will link to your navigation app (Google Maps, Tom-Tom etc.) so that you can get direction to a location.  It is more accurate than postcodes, which usually cover several houses, and is especially useful out in the countryside where postcodes can cover a very large area.