it beats rubbing the hairs on the back of your hand.
I could never get that trick to work, but then I don't have any hairs on the backs of my hands (or the palms!

)
Have you been inside the unit? - is it just a speaker in fancy box?
I will have to see if we can get a trial, it would certainly make testing the foetal monitors easier.
Cheers for the info,
Rob.