MapMyRun-- Map out your route, track your activity, keep a log of food and you can even share with friends. You'll find both a web and app version along with MapMyWalk, MapMyRide etc., personally I don't think it would matter which one you use, as you can change your activity that you are doing. I use this one to track every walk and run and to even map out a new route.

Classroom use: Students could keep track of the number of steps they take in a day at school. This could be used for creating charts and analyzing data. Do we walk more on different days of the week? How many steps from our classroom to the computer lab?

For Kids:

Classroom use: Any and all classes when you just need a moment to relax and refocus. This may come in handy since testing season is upon us.
And one that I'm tempted to try out but haven't yet, (it costs $3.99) is Zombies, Run! With this app you listen to a story and there are certain times you have to run to complete quests as zombies snarl at your heal. Sounds like a fun way to get a run in to me.