As you probably know, the iPhone3GS's processor is based on the ARM Cortex-A8 architecture which is quite capable of recording HD video (for more information on the CPU war check out our article on the topic). For some reason, Apple imposed software limitations that don't allow the end consumer to record HD video with their iPhone 3GS. But not anymore, since all you have to do is to follow a few instructions which can be found in the first link at the end of the article.
Sounds all good really and the jump from 640x480 to 1080×800 at 30fps is quite a big one. In order to do it, download the pre-edited file HDVideo3GS.zip and follow the instructions in the links below. If you take this step, then let us know how it works.
And just to see the difference, the video below is recorded in HD by an iPhone 3GS after the crack.
source: Mike's Blog via Into Mobile