NB When in Scottish mountains I take:
- An iPhone with offline OS maps
- An external battery for my iPhone and cable
- A paper OS map in a waterproof map case
- A printed A4 backup of an OS map in a plastic bag that I can give to others or to use if other maps become unusable (e.g. blown away - which has happened)
80% of the time I just use the iPhone - still have to use OS map and compass occasionally when things are particularly exciting.