Call Block is a useful tool for blocking unwanted incoming or outgoing calls, including:
- blocking all numbers
- blocking numbers that are hidden / private
- blocking all unknown numbers - effectively allow only numbers that are in the contact list
- blocking any number you want by specifying it directly
- viewing logs of blocked calls

Now in the latest version you can also specify number list which will be allowed regardless the other blocking settings. This is useful if for example you want to block all unknown numbers but allow specific numbers (eg. emergency numbers or the ones starting with the given prefix)