This is a good one thanks to Lifehack for Apple users::
Google Maps as a Free GPS
While travelling abroad, you can use Google Maps as a free GPS without an international data plan. While offline, simply zooming to a map area you want in the maps app, and type “ok maps” into the search box. This data will be available even when you do not have data connectivity.
There's more helpful iPhone and iPad tips on here:
Top 24 Useful Tricks of iPhone and iPad Most People Don't Know