'Two wheeled cars' have been built before, the Ecomobile being the most famous. However, the C-1's unique selling point is that it stays upright when stopped without outrigger wheels. It acheives this by having rotating flywheels built into the floor to give a gyroscope effect.
Here's a couple of videos that explain it better:
Interesting idea, but like most designs like this, will probably be extremely rare due to high price and customer resistance to 'something weird'. More on the company website, but whether we ever see one on the road remains to be seen.