Stefan Esser, better known as I0n1c has put together a rather detailed presentation on the latest iOS jailbreak techniques. The presentation was made recently at Black Hat 2011 in Las Vegas. The presentation consists of 97 slides in total covering subjects like Kernel Debugging, Kernel Exploitation and Kernelpatches from jailbreaks.
The iPhone user land is locked down very tightly by kernel level protections. Therefore any sophisticated attack has to include a kernel exploit in order to completely compromise the device. Because of this our previous session titled "Targeting the iOS Kernel" already discussed how to reverse the iOS kernel in order to find kernel security vulnerabilities. Exploitation of iOS kernel vulnerabilities has not been discussed yet.
To be honest, this is way over my head but if you do have an interest in this area and want to take a look at the presentation in its entirety, you can download it here.