Silent Guard is an app that simplifies silent mode.
There are three customizable buttons that will take you in to, and out of silent mode(vibrate) for the specified time. Simply press and hold a button to change its value, there is also a widget containing those buttons.
Night Mode takes you phone will go into silent mode(silent) between the specified times for the specified days,
Auto Silence takes you in and out of silent mode(vibrate), and you have the option of taking pauses from silent mode.
You can also chose which contacts can call you through silent mode (like emergency contacts).
Silent Guard gives a notification in your statusbar when it has taken your phone into silent mode and will automaticly start your scheduled silent modes when the phone is turned on.
Sony Xperia battery optimization disrupts scheduled silence modes unless you whitelist Silent Guard or refrain from using their battery optimization.