Settings Watch may come in handy for advanced Android users, who are willing to track changes of and customize the settings of Android OS. It can store the current state of configuration and, if any changes were made, display the differences.
This App displays the values as stored in the setting's database. In order to edit specific items you are required to know what values are valid. The information can be found in Android SDK documentation: http://developer.android.com/reference/android/provider/Settings.System.html, http://developer.android.com/reference/android/provider/Settings.Secure.html.
Some of the changes only take affect after rebooting the OS.
Disclaimer: I take no responsibility if careless modification of values causes Android operating system, component of it or other application to stop working or behave incorrectly. Please be careful.