There is a new vulnerability with iOS5 powered device with a SIM card. I have tried it and it works.
You need to know the number of your victim and by combining a missed called, removing the SIM card, putting it back in and swiping the missed call alert it is possible to bypass the lock screen and access the phone.

Look at the video from the weirdly named group called iPhoneIslam, you need to get the timing right!

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