Advancer Technologies built real Wolverine like claws that extend when you flex. They actually provide a tutorial for you to make them yourself too.
Our tutorial will teach you to build bionic claws using our fourth-generation muscle sensor, the MyoWare. Simply flex your forearm muscle and *SNIKT*, a fraction of a second later the 4 inch claws extend out. Relax your forearm to retract the claws. We've even added a muscle-activated locking mechanism in case you want the claws to stay out without keeping your muscle flexed.