Amusingly, helium is a fossil gas. (It's extracted from the top of natural gas reservoirs.) Once we run out, there won't be any more, and the only way to make more is through nuclear transmutation, or extraterrestrial mining. No matter how you look at it, filling balloons with helium and giving them to children is going to be too expensive in the near-ish future.<p>Also, attaching an iPhone to a weather balloon seems like an expensive and roundabout method to destroy a phone, if the parachute fails, or if it hits water hard enough to break the seal on the instrumentation capsule.