Kinetic energy use: future or gimmick?

Putting the details of the laws of physics aside (kinetic energy, accelerating body to reach velocity, etc.), this type of energy resource seems largely infinite (add to wind, water, solar energy). It seems traditional to have new and largely unexplored sources of energy be tested on small things (such as the new Infinity Cell for the iPhone) (read http://bnn-news.com/infinity-cell-lets-charge-iphone-simply-shaking-93676 for some details if you like). But is there really a solid future for such energy?
I believe these things should be used to power small electrical appliances like flashlights, wrist watches, cellphones. This can be pretty handy when travelling, hiking or having a morning run.