Startup Idea : solar power phone charging

my come in two ways here... ok so... There is nothing more annoying then your phone dying when your on the road! Lets say your at a festival and you have to search around just so you can charge your phone... well with the solar power phone charge you could be in the comfort of your tent and simply pitch in the ground outside your tent and the nature do the rest. Here another one maybe your at just at the pub with you friends chatting and facebooking away and you see the 10% battery icon, annoying right? and its only 2pm. i would design a iPhone/android case just like the external battery but with a sheet of solar panel to keep the case charging. this case would have a on/off button for the panels. this could also help save lives of travellers, hikers, etc. because this is away of helping of getting back communication with the world if your in trouble or in other cases you use your phone to much like me.