Aptupdate for SBSettings
Using this toggle you can updates and upgrades your Apt cache and packages in the background and this was the first toggle to appear in Cydia. Simply you have to press the button and then you can do anything while iPhone updates.
Debian Updater for SBSettings
This toggle comes with a Status Bar icon which allows you to know when its running. A separate Status Bar icon will be shown when it finds any updates. Without starting Cydia app you can refresh your Cydia source list on lockscreen, or Springboard.
You should note that before installing the above toggles you must install SBSettings from Cydia.You should remember your iPhone, iPod touch and iPad must be jailbroken to install it. You can follow the steps posted here to jailbreak your iPhone, iPod touch and iPad on iOS 4.2.1 with Redsn0w. [Via]