What it is
An iPhone app for creating and drawing the specific route you want to run—and then going out and running it. You sketch the route on the map, tweak it until the distance and shape are what you had in mind, and take it with you.
Where it really earns its place is running together. Plan a route with a buddy around a meetup point: you each get your own leg to reach it, run the shared stretch from there together, and split off again towards home at the end—all worked out up front instead of improvised at the corner.