
Install AppSync 4.2 for iOS 4.2.1 from Cydia – How to Guide
The Appsync 4.2 is now available from Cydia to download that is compatible with iPad, iPhone and iPod Touch running firmware 4.2.1. The update will patch the MobileSubstrate installion allowing you to manually install .ipa files directly from your computer. AppSync requires a jailbroken device.