Pod2g has confirmed in one of his tweet that he has performed untethered jailbreak on his iPhone 4 on iOS 5.1.
Heya! My iPhone 4 running iOS 5.1 is now untethered
Earlier, he revealed that he has discovered two big vulnerabilities in iOS 5.1 and must have used them to perform untethered jailbreak on his iPhone 4 running on iOS 5.1.
He had also asked in his official blog to his followers whether he should release jailbreak for iOS 5.1 or wait.
Pod2g has however, not posted any screenshot of his jailbroken iPhone 4 or a video and nor there is any detail regarding the public release of untethered jailbreak on iOS 5.1.