Apple has just released the first beta of firmware 4.1 iPhone iPhone 4, iPhone 3G, 3G S and iPod Touch second and third generation. Surprisingly iPad version is still unavailable. iOS 4.1 Beta 1 contains the new modem firmware, if you are looking for unlock in future then stay away until Dev-Team confirms. iOS 4.1 is pushed to fix iPhone 4 reception (Death Grip) issue, according to macrumors the new signal bars appear slightly taller than the previous ones, and presumably Apple’s calculations regarding signal strength has been revised.
Registered developers can download via their developer account developer.apple.com.