I have the Z2 by Breas. It's OK. Not as good as my full sized Airsense that everybody has, but it does the job. The one thing I don't like is the reporting software is crap. The Airsense gives you those nice progress stats, and you would think that I only use my travel device an hour a night.

Edit. To the OP: What is the Z2 by Human Design? Are you sure it is not the Breas?