Pr4100 - Pen AS a key to unlock HDDs

Is it possible to save the encription password into a PEN.

But, is it possible to use a pen, with the encryption key on it, as a key locker?!
The idea is to insert the pen and start the NAS, that automatically unlocks the encrytped drives…
(My cliente had a Netgear NAS that had that function… and he wants it!!!)
Can some one help?