Etnier and Mjm_analog,
Thanks for those links. This looks much like an ultrasonic RCM that John Chapman of BentAudio was beta testing 9-10 years ago. I *almost* got one, but John had to drop the project to focus on other concerns.
BentAudio never brought theirs to market. It's good to see someone picked up the concept and is trying to make it viable. Very tempting, especially at that price.