There are offline apps that work even without a GSM or Wifi network. It's actually possible to create a smartphone 'digital toolkit', which can be very handy for tourists.
Maps.me is an interesting alternative to Google Maps, which offers hiking routes. Park4night is for lovers of classic campsites and wild camping, as well as motorhome users looking for good places to park overnight. Currency Converter Plus allows you to convert nearly 160 currencies, from the Kenyan shilling to the Sri Lankan rupee.