SlideForUsage is a new Cydia tweak that takes advantage of all the extra canvas in order to display info about open apps in the App Switcher. While in the App Switcher, slide down on the apps to see information on usage: time since last launch, time spent in last session, total time spent in app since tweak was installed.  Also you can slide down on the SpringBoard card to get time since last reboot.

You can download SlideForUsage for free in Cydia via the ModMyi repo.

source [FSM]