The Signa bike runs on fuel cells. But instead of making you carry hydrogen next to your butt, it uses a new, clever, safer method: It runs on cells full of a sand-like powder. You just have to add water.
The powder is sodium silicide, a safe substance that is not dangerous at all. When you add water to the cell, hydrogen gas is produced, which generates electricity. The cells weigh 1.5 pounds and they are hot-swappable. This means that you can easily plug in a new one after you reach its maximum 30-mile run.
According to the company, they are working in making these cells more powerful, so they could be integrated in cars. [Wired]