I've often thought that rear view mirrors would make excellent places to fit less-relevant info, look at augmented reality systems that such as Jag are looking into at present. Basically living your life like driving in a real-life video game with all manner of alerts, signage, readouts and other info hopping up on your smart glasses at every second of the day.
Personally I think any extra stuff, no matter the good motives (safety, primarily) only mean you are more and more distracted from the road. When the mind in bombarded with too much info it stops paying attentio. You can, and will have a bright red flashing light right in your face saying 'warning, pedestrian being dragged under the vehicle' and if it's accompanied with a dozen other notices/facebook updates etc, you will not realise it's there. Ever been at a noisy party and someone is literally shouting your name next to you and you jump and realise what they're doing? Because we like to pay attention to one thing at a time. It's how all magic tricks work, your attention can only be at one place at any time.