How do Balloons travel?
Balloons! uses your iPhone's location services to work out where you are launching your balloon from. The black box then works out speed and direction of travel. If another Balloons! user tries to catch a balloon and yours is one that is in range then yours has a chance of being the one that they catch.
But how does the black box take notice of winds, the earth's rotation, etc etc? That would be telling....

