The long arm of the pen

I've just been reading about a technology that was apparently conceptualised by the author Margaret Atwood. It allows authors to sign copies of their books remotely...and the signature is legally valid. LongPen, operated by the company Unotchit (you no touch it) is a pen that operates over the Internet. The book is be placed down on the machine and the author, sitting in the comfort of their own home, can sign the book from where they are. The LongPen moves over the book as if by magic. In addition, there is a video link so that they can talk to their fans. The advantages are clear, not least the reduction in travel. This is certainly the greener way to enjoy book signings, and of course it has many other applications. What I find particularly interesting is that this kind of traditional, but actually truly digital signature, is legally valid. I wonder if LongPen signatures will fetch the same price in the decades to come that the signatures on old documents fetch now? And does a LongPen signature on a digital document make the document unique?