[nemeth88]

Windows Phone does this - when paired with a list of specified Bluetooth devices (such as a car GPS or stereo), it can switch to a DND mode automatically with an optional auto-reply.

Motorola seems to have recently rolled out a similar feature across it's entire Moto G/E/X product line - Drive Mode for their Moto Assist product.

But unless these kind of features become opt-out, I suspect it won't help that much. Right now you have to actively seek them out and turn them on, which many people aren't going to do.