A system for restricting uses of moving phones used by drivers, but not passenger phones, and sometimes interrupting voice calls, including: (a) Provide for more than one level or state of restriction. (b) When a caller calls a person driving, play to the caller a query whether the call is important enough to put through, and put it through only if the caller responds affirmatively. (c) The phone is restricted in functionality when the vehicle is determined to be experiencing acceleration greater than a threshold. The restricting may be to play an alert sound to be heard by people listening to a voice conversation on the phone. The restricting may be to suspend a voice conversation on the phone.