Both Android and iOS have "Do Not Disturb" features which almost accomplish this. On my Android phone, the "Priority only" setting will silence any calls from

Both Android and iOS have "Do Not Disturb" features which almost accomplish this. On my Android phone, the "Priority only" setting will silence any calls from outside your contacts list. It would be ideal to be able to send directly to VM, but this option definitely minimizes the distraction. I have it enabled 24/7, except when I know I'm expecting a call from an unknown number.