These products have a solar cell technology which "uses a photosensitive dye to start its energy production, much the way leaves use chlorophyll to begin photosynthesis."
You can recharge your phone in your bag! You could recharge your e-reader in its case! How kewl is that?!?
Check out this great article in the New York Times for other applications.
Or if yo're dying to know how this works, check out G24 Innovations -- the company developing the technology.
Hopefully these won't be priced out of the market for us normal folks.