Backgrounder has been updated and now on Cydia you Store
find the version compatible with IOS 4.2.1. There has also been
also added other interesting features.
Backgrounder app that allows you to control much more effective applications that run in the background. In practice the user will be whether a given app will continue to work or if you prefer to be disabled once returned to the home screen.
Backgrounder is a Mobile Substrate-based extension to iPhone/iPod Touch’s SpringBoard application launcher that allows applications to run in the background (applications are normally terminated upon suspension).
Enable backgrounding for an application
Backgrounding can be enabled via one of two methods:
To enable backgrounding for the currently-running instance of an application, press and hold the menu/home button until a message pops-up stating “Backgrounding Enabled”.