It's finally here, folks. The Chronic Dev Team has put out the latest version of greenpois0n that allows you to free your iDevice running 4.2.1. What's different about this jailbreak? Glad you asked. This time 'round, the program will let you perform an untethered jailbreak -- you can finally reboot the device without having to re-jailbreak. Be warned though -- this build was rushed out and we haven't tested any devices on our end. At the time of this writing, the software is only available for Mac. Oh, and unlockers, don't update to 4.2.1 if you plan on swapping sim cards in the future. Hit the source link to get started.