InteVyDis has released an untethered jailbreak for A4 devices on iOS 5.1.1 as part of Vulndisco Mobile 1.7. The module is vd_ios_untether_5_1_1. It works by creating a custom bundle you have to install via RedSn0w. Evgeny Legerov posted in twitter:
vulndisco mobile 1.7 is out with untethered 5.1.1
This jailbreak is not free and costs big money. It works only on A4 devices -- iPhone 3GS,
@legerov runs a company: Intevydis that sell exploit packs for many years. If that JB were fake he would hurt his own business.
The unfortunate thing is that now two sets of exploits may be revealed to Apple and some people may pay for the expensive exploit pack despite it being available free in a few days from pod2g.
the most troublesome part is that (potentially) close to 2x as many exploits will be burned now with 2 A4 JBs.
We recommend that you wait the extra day or two for a free jailbreak from pod2g that should work on all devices.
Here is a video demo of this jailbreak.