Hello
You guys will have already seen this but just in case...
I found Map Tools by Clever Applications on Apples App Store. The free version translates formats and datums, but you pay £1.99 to get access to 'all' of the datums and options.
So for example it converts UTM to different Lat/Long formats and vice versa on WGS84, or Ordnance 36 Eng and Wales Grid refs to Lat/Long WGS 84... or whatever datum and formats you wish to convert. There are probably loads of these tools but this is easy to use and works offline so when you are out in the sticks with no internet it still works.