People have been wishing for and trying to do this for a while. Solar panels get better all the time and it may become reality. The issue is, last time I checked (I am not up-to-date), that you need the sun directly impinging on the panel. A slight angle off of 90 degrees (between panel and incoming light) kills the panel. Walking around all day, your panel will rarely be positioned correctly. A well designed panel will result in little to no charging. A cheap panel will drain the thing it is supposed to be charging.

You can get the same effect for less money and it actually works by bringing a rechargeable battery pack and then charge it (at home) with a renewable power supply (purchased from your power company or home installed panels).