Pyro Paul said:i also doubt the Devs acctually got the idea from a 'punching blade'
the 'WristBlade' has been around for a long time and has been used in many forms by enthusiests, hollywood, and outlaws to have a consealable weapon in easy reach. the first memorable example of a Wristblade would be in the movie 'Hudson Hawk' (1991); a light action comedy box office flop staring bruce willis. during the end the butler produces 2 wrist mounted switch blades which, while wholey impractical, are shear awsome.
I would hate to say they were 100% inspired by a punchblade (as nothing is 100% inspired from one thing - that would be copying) - although they said some inspiration from the Katara; an Ancient Middle eastern/Indian weapon.