Pretty much what I've been saying for a while:
Step 1. try to "sell" it to the populus as something that will bring insurance premiums down, and provide good evidence of what really happened in (and just before) a crash.
Step 2. Offer insurance discounts for those who voluntarily adopt it.
Step 3. Make it mandatory fitment to all vehicles.
Step 4. Make it an offence to disable or tamper with it.
Step 5. Go completely over-the-top. Forget about any USEFUL application, and simply link it to the sat-nav to use it for automatic debiting of bank accounts and adding of points to licenses every time a speed limit is exceeded. Why stop there? Use it for road charging too - and parking infringements!
Oh, and don't kid yourselves when it says "only a handful of manufacturers record this data". Aye, right...

Only a handful of manufacturers ADMIT to recording ALL OF this data! For at least the last 10 years, pretty much all cars have been able to record a lot of it! At present the manufacturers only use it to defend themselves when someone tries to claim the car malfunctioned...