DDM (Don't Disturb Me) is an application which allows you to turn of the ringer of your Android phone for particular incoming numbers and (if you want) in particular days and/or times.
It allows to choose a number from your contacts or to specify manually the number. Also, it let you set (if you want) which days and/or which times of a day you want a call of this number(s) to be silent. When you define and apply your settings, DDM checks each incoming call and if it finds a matching entry for it, turns the ringer of the phone in silent mode. When the call ends, the phone ringer is restored in it's previous state.
DDM is an application that can help you when you don't want some incoming calls to disturb you: always (e.g. your...ex- for example), in particular days (during..sleep), in particular times (during weekends, meetings, etc.).

Screenshots: