I can't count how many times I've thought of the usefulness of a system as described by the grandparent comment. The best I can come up with so far is some kin

I can't count how many times I've thought of the usefulness of a system as described by the grandparent comment. The best I can come up with so far is some kind of dedicated screen, with always-on audio capabilities similar to dash instrumentation, made mandatory in all vehicles and accessible via an open wireless protocol (possibly a hybrid of different signaling mechanisms like wifi and infrared signals). These signals could be prioritized for emergency vehicles using a special FCC-controlled frequency/protocol and rate-limited to prevent abuses. A big potentially insurmountable issue is exploitation of the emergency services protocol, so that part might be wishful thinking. Unfortunately without it the system seems like it would end up as more of a nuisance in many peoples' minds, and would never be legislated as mandatory.