The absolute biggest complaint I have with smartphones is battery life. There are plenty of ways to deal with that, of course, such as turning down your brightness and turning off your connectivity, but who really wants to do that? You can't work that way.
How you combat that whole "not doing work" problem is usually solved by extra batteries, or maybe a case with a battery installed. But there's also one other way: harness the energy of that blisteringly hot sun.
XTE will possibly give it another shot sometime with their Solar X500 smartphone. They've already done it with a few other phones, but what makes this one interesting is the fact that it's a smartphone. Zagg leaked this new device, though it's possible that it won't ever be more than just an image. XTE usually uses three of the four buttons out of the Android button array, and this one is using all of them. Also, in searching through the FCC's database, you won't find the X500 anywhere.
I don't know much about your phones' lifestyles, but for mine, they spend 80% of their lives in my pockets, coming out for email, texting, and Angry Birds. Hopefully XTE has thought about that before they put this little guy into production.[Pocketnow]