Yup..appart from the normal googlemaps or Bing Maps if you have unlimited data and good reception as bing also have fresh new OS mapping/road satnav type and sat imagry to choose from.
There is also Memory Map that has a free trial download for the i-phone/i-pad.. (Also for android smart phones) if you like it then buy the MemoryMap UK maps for about £100..
You can share routes..do all your planning on the PC/Mac and then simply transfer/download the area with the route to the phone and away you go using the phones built in GPS...
The alternative is ViewRanger.. I use this most of the time and it works a bit like MM.
But now MemoryMap has a phone app it might just beat it....
Get a proper otterbox cover for it..http://shop.memory-map.co.uk/acatalog/i ... ender.html