iPhone Dev Team has released Redsn0w 0.9.15b3 for jailbreak iOS 6 Tethered with having Cydia and ability to restore to older firmware not being signed by Apple for all A4 and A5 device like iPhone 4s , iPad 3 if you don’t upgrade to iOS 6 .
update : iPhone 4 GSM 9B208 Added
There is a simple way to update to iOS 5.1.1 without basebande update to use Gevey sim or unlock with Ultrasn0w if you can . easy unlock and jailbreak . Its a untethered jailbreak .