Updating my 3GS from iOS 4.1 to 6.1.6 Is there a way i can upgrade my iPhone 3GS from iOS 4.1 to 6.1.6 without using a computer?
In short, no.

OTA [Over the Air] updates are only available on devices that shipped with iOS 5 or later.
Your only alternative is a computer running iTunes.

Source: Wikipedia - iOS