i had the sbsettings on my jb before i switched to ios5 5 so i dont know if it carried this feature over some how or not.
when i touch the reception bars on my att iphone 4 on ios5 it will change to show decibels. if you open a app you can either turn db on or off and it will remember the setting every time i open the app.
This carried over because you restored from a backup. The only way to enable it on a new install is to access the field test, and kill that app, the old-school way.
