Integrate it with your speedometer, look ahead on your GPS route, factor in time of day vs. likelihood of presence of law enforcement, take into account accident data and risk based on location and time of day, and rather than a HUD, simply have an ambient dash light that boils it all down and glows related to your risk. Integrate GPS+radar detector+Whispernet (real-time wardriving for speed traps).
I'm sure with the radar detector this would already break laws in about 30 states, but the core idea still would be viable if all you did was integrate crash data to alert people to risks in areas where their perception of risk was off.
If they remake the movie "The Gumball Rally" again in a few years, I'd expect to see this device featured by one of the teams.
