Can you clock off some distance using a running machine? Or do you have to be outside.
You have to have GPS movement - a running machine won't work. Technically you don't have to even be outside, but you'll obviously get much better GPS reception outside.
I often leave my app open and get small amounts of 'walking' from the GPS re-fixing its position. It's not a lot, but it helps get a bit closer to the eggs hatching.
In addition, remember there is a speed limit - so driving, taking the train etc. is only going to count when moving real slow.