This is something that Nokia has been working on for some time, as demonstrated by the filing of this patent in early 2010, but the general idea goes back much further. There are quite a few chargers that allow you to use kinetic energy to recharge your phone, such as Nokia Bike Charger accessory, but the next step innovation is making some that works during day-to-day activity (i.e. walking, or dancing, around) and is small enough to fit inside a phone.
The prototype demoed in the video is getting close to that goal, but there's still some way to go, as is ably demonstrated in the video... you need to do a lot of dancing to get a significant amount of energy.
The kinetic system isn't the only approach Nokia is working on. For example, another research project is investigating the way in which energy might collected from ambient radio waves, and Nokia's Morph concept foresees devices being covered with "nanograss" structures that harvest solar power.
Ultimately, none of these methods are likely, in the immediate future, to result in a device that never runs out of a charge, but the idea of a device that can stay in a permanent stand-by state (i.e. trickle charging when device is inactive) may not be so far away.
The video is part of a wider campaign that is seeking to promotes Nokia's sustainability and environmental initiatives and policies. Nokia is encouraging people to join share their thoughts via the #sustainablelumia Twitter hash tag.