At first, Locus may seem just like a stock iOS 8 feature; however, Locus only turns on location services when your whitelisted app has been opened. Then, when the app is closed, location services are turned off, and ultimately, battery life is saved. In iOS 8, some apps let you restrict location services to "While Using App," but many devs have yet to include this feature.
For instance, if you keep always keep location services off, but want one app, such as Apple Maps to use your location, then this tweak would let you to do just that. Locus also has a toggle for notification center so that certain widgets that use your location (such as Weather), will still work.
Locus is available for free in Cydia from the BigBoss Cydia Repository.
Please follow iClarified on Twitter, Facebook, Google+, or RSS for more tweaks!