The band has a membrane running through it that could be made of silicone that would snap around the wrist. The outside would be a more durable form of rubber.
The device above can be used to cut steak for people with one arm. It would use high quality metal blades as well as durable plastic to withstand hard hits to cut the meat at the base. Clear plastic would be used around base so you can monitor the cut.
The Bracelet uses a membrane made of silicone that snaps and wraps around. It could be decorate with diamonds, gold, silver etc.
The device shown helps crack salt and pepper. Would use Metal blades, plastic and clear plastic as well.