The Chronic Dev Team have just released an untethered update to their greenpois0n jailbreak software, successfully jailbreaking iOS 4.2.1 using an untethered exploit method. It is available free to download at the following websites:
Downloads:
Main Website -- http://www.greenpois0n.com
Mirror Site -- http://alnandr.net/greenpois0n_mirror
This video features the newly released MyWi tethering app available only to jailbreakers though Cydia. The app now has a smaller battery footprint, an iPad app companion, and a new “Set and Forget” feature that throttles the amount of tethering ( internet sharing) between your phone and another device depeinging on how much data the device is requesting (saving a considerable amount of battery life).