How do you feel about using rings to open doors and paying for things? It's fashionable, and you'll never lose them, unless you take them out.

This is the Sesame Ring. The wearable Charlie Cards can get you around because they are implanted with RFID tags so all you need to do is tap the sensor when you're boarding the train. It's a fantastic idea. Imagine the Touch n Go card being replaced with this.

You can also reload the ring like how you would a prepaid card. The ring here is already integrated on the entire MBTA system in Boston, but the team of MIT students plan to spread the technology around the world.

Look, even Tony Stark is using one. [The Atlantic Cities via Archinect]