You beat me to the punch... I was on my way to this site to post a question that I had about the Knife Thru Arm effect.
I need to know about the version that the Amazing Jonathan has advertised. It's a Knife Thru Arm that apparently is of his own design. If it's the one, and it probably is, that he uses on his TV Specials then it looks great. Unfortunately, there is no picture and the ad copy on the site is minimal at best.
I've sent an email to the site requesting more info but I have yet to hear back from them. If anyone out there knows about this product or is lucky enough to own one, then I'd like to hear more. Thanks