Several months ago I installed Zombies, Run!
on my phone but as I hadn't been going out for walks or anything, haven't actually used it. FH and I went for a walk again today and I decided to use it! It's kind of fun; it tells a story as you go and you pick up supplies along the way that help the town. You can also choose whether or not to have zombie chasing - randomly during our walk it would tell us that there were zombies approaching and to run run run! I don't really know what happens if the zombies catch you - it happened to us once because we didn't really hear it, but it didn't
It uses GPS to determine your speed and distance, and actually maps it out on a map on your profile... It's kind of creepy because it was really accurate with our path, usually I find things using GPS are only an estimate and may or may not be correct. This had everything!
Our favourite path at the moment is about 4.2km; I think if we cross another road to another section of park and paths we could probably push it to 5km. Maybe once it's less painful I'll consider it, I am in a world of pain