The latest Hammacher-Schlemmer catalog offers a hot air balloon for $49,000. The description of what you get includes an airspeed indicator. Since the airspeed of a balloon is zero, except for gusts, what is this thing? One thought that occurred to me was that it's really a ground-speed indicator, using a GPS, which would tell you how fast the air mass you're in is moving, which I suppose might be useful. But that would be an odd use of words, unless maybe balloon people have their own jargon. Anybody know?