Well, batteries have improved a lot, but nothing like the orders of magnitude that we've seen in the computer industry. Doubling the capabilities of batteries doesn't happen so often, but doubling storage capacity happened a lot, for instance when we went from 1TB drives to 2TB drives in a single iteration.
I dunno, rechargeable batteries is one of the biggest innovations in handheld anything
I think what people are mucking about tho, isn't so much innovation, but paradigm shifting technologies
adding more whizbang, while innovative at that individual whatsit level is great, it doesn't change how an item is used really. adding more memory, or more battery doesn't change how I use my phone
adding bluetooth tho did change how/when I could use my phone
adding accelerometers and gps changed/innovated how it was used, even tho they were common technologies somewhere else
so you're equally right saying the new iphone has some innovations on it that make it better than last years, but at the same time, it's just an incremental refresh that doesn't change anything