Tim Bray has some interesting things to say in Answer the Phone Call, a commentary on where to find opportunities in the tough times ahead. Whilst I broadly agree with his analysis - more phones are sold every minute than there are people born, and there's far more innovation in mobile than on desktop at the minute - I disagree with one of his points:
This year, with the advent of the iPhone and now Android, there is a large and rapidly-increasing number of highly-programmable devices out there, which (and this is new) don't have moronic, blinkered, old-school mobile network operators erecting barbed-wire fences between developers and the people who actually buy phones.
I left a comment, but I'll add it here as well:
You're right in that the mobile market is a good place to look for opportunities - especially with the rise of the smart phone and the mobile always-on all you can eat internet. But it's misguided to suggest the iPhone and Android alleviate the barriers to development erected by network operators: many of these barriers still exist (as exemplified by the fact that neither of the phones you cite will let you any nearer the "bare metal" than you can get with all the other platforms).
Beware, also, where you seek your opportunities in the telecoms market. The previous commenter suggests SMS, but with the always-on network this is going to decline rapidly in favour of email, mobile instant messaging clients, and social networks, all of which have significantly less cost and far greater functionality.