SPMA9589 is the product number for the Spektrum Variometer telemetry sensor. It available all over Europe, but there's no hint of it here in the USA. Pictures of it on the web indicate it is a barometric sensor, of course.
Perhaps someone who has one would care to share their observations? Like, what kind of tones does the system emit? Is a firmware update required? Are there problems with it, a possible reason for its non-release here?
Also, perhaps a representative or someone in the know at Spektrum could share a release date, or a reason why it is not available domestically?
After all, if it was infeasible to produce one, one wouldn't already exist. Spektrum, we want one!