I've said all along that the Walkmeter App is great for recording walks but not for use as a mapping or locating tool due to the reliability of it when there's no phone reception or service.
Whilst I was training for the Oxfam Trailtrekker I set the Walkmeter running and off I went. Not long into the walk I went to make a call and not really surprising on the 3 network, there was no service at all not 3G. Checking the Walkmeter App expecting it to have conked out. No, it was still going strong so I can only assume that my iPhone has some sort of GPS chip in it to enable it to continue to function without any connection to the Internet.
I still feel though that whilst the Walkmeter App works without Internet connection it is still really any good for recording routes as its format is in satellite view but could potentially be difficult to cross reference with an ordnance survey map. The Satmap Active 10 however gives you a grid ref number so I would stick with this for navigation and identifying where exactly you are when out on the hill.