Meet the Alpha ring: a nickel-free titanium NFC ring you can use to unlock doors, interact with your phone, and even share information. It comes in at about 13mm wide. Since this is a NFC ring, you don’t have to worry about recharging its battery. Just bring your NFC compatible device, and you are set. You can even use this to interact with your Arduino and other creations. Sets you back £34.99.