Aside from the headline features of Android 4.3, Google also has a couple of hidden features in its latest Android version that weren't talked about. The more significant of the two discovered so far is known as App Ops.
Buried within the Package Installer, App Ops allows you to turn off several permissions of apps running on the device. According to Android Police, the feature is not really ready yet even though it appears to be working.
App Ops gives you an overview of the apps and services running on your device, and categorizes them into four tabs: location, personal, messaging and device. Below each app or service is a brief description of the permissions that you have given to it. There is also a time stamp on the right to inform you when the app last used a permission.
In the screenshot above, you can toggle the permissions for the Facebook app. For example, if you do not want Facebook to know your location, you can disable (or "off" the switch) for location.
Appaholics, an app developer has come up with an app to allow direct access to this hidden feature. The free app, Permission Manager is a shortcut to App Ops and is available for Android 4.3 devices. It does not require root or any special permissions.
App Ops in general benefits users as they can identify misbehaving apps that regularly ping their locations and drain the battery. It also gives users more control over their privacy. You have to take note that by turning off certain permissions for an app, it may not function properly as you are "messing with settings the app developer never intended for you to have control over".
Nonetheless, App Ops should force developers to be more open about what their apps actually do and have access to. It is definitely a step in the right direction towards good privacy practices on mobile devices.