@Barney. Did you ever get the chance to try any of them on a Fluke / Rigel / SimCube / SmartArm - or whatever - tester?
Using kit like that, at least the test regime can claim to be consistent; and also show that these units are just as "good" (or bad) as any other non-invasive method of measuring blood pressure!
PS: I've just realised (found out) who you are, Barney. Although had I been a bit more "alert", I should have realised from your first (Sep-07) post! So I had better add:- Cheers, Mate!