Contrary to what you may think, clearing or swiping away apps in the Recent Apps view on your Android device does not necessarily stop app activity or running tasks—and these running processes can actually be eating away at your battery life. Depending on the app or process, it may only be a small percentage, but every little bit helps these days.
In order to ensure that you're actually killing an app and its background activity, install App Hypnotist from YirgaLAB. This app not only "hypnotizes" running background processes, it also displays the potential data and battery life saved by doing so.
Update: As brought to our attention by member Melvin, the app has changed names to ShutApp—our link has been updated.
When you first open App Hypnotist, you'll be required to enable accessibility services for it. Tap Open Service, then locate App Hypnotist under the Services header and toggle it on.
Step 2: Whitelist Preferred Apps
Whitelisting certain apps will prevent App Hypnotist from killing them. You should whitelist things like live wallpapers and music services—basically anything that you want to persist. Just enter the app list through the three-dot menu, select an application, then hit Add.
Step 3: Hypnotize Your Apps
Tap the large Hypnotize button to begin killing apps, after which you'll see a Done screen with information on how much battery and network data was saved.
App Hypnotist is free, simple to use, and doesn't require root. Let us know what kind of results you're getting in the comments below, as well as on Facebook and Twitter.