First question I have is it UL rated, what is the rating and how much fire will it extinguish? After 35 yrs in the fire service I have found that vehicle fires usually occur in a confined area and none of them would have been accessible with this device. If you decided to open up the involved area and toss this in you'll stand a good chance of getting burned as the fire gets more O2 and flairs up. This unit might have some use as a fixed fire protection system. Like all of those systems they need at least annual or semi annual maintenance.
If you have it mounted over the stove or in the engine compartment what tempature does it discharge? Is the tempature sensing unit subject sensitizing when exposed to moderate heat and will it discharge prematurly? Is it going to be able to control the fire, will it activate in different areas of the engine compartment and provide coverage for the whole area? Will the engine fan just blow all the agent away too fast? If it doesn't knock the fire down what's your back up plan?
For the cost of one of these units you can buy two or three UL listed 3A-40 B,C fire extinguishers. You can probably go by your local fire department and ask for a lesson on how to use your extinguisher properly. They should be more than willing to help you with any questions you have. If you're willing to use your own extinguisher (buy ones with a metal head they are refillable) they might even light off a fire pan with flammable liquids in it and let you put it out.
If you noticed on their video they are tossing the unit into situations that you have easy access to a free burning fire. If they tried that on a car fire with the hood down it couldn't get to the seat of the fire and you'd have powder all over the outside of the car as the fire merrily burned away under the hood. If you open the hood you'd get a face full of flames.
My recommondations are to buy two-three 3-A, 40-B,C dry chem extinguishers mount them around the various areas of the coach. Learn how to do annual inspections on them and do it more often because you drive around. Learn how to use them with hands on training. Call 911 from outside and safe distance from the fire BEFORE you try and save the day.
Note: How UL rates fire extinguishers A- ordinary combusitbles wood, paper, etc, B- flammable liquids, C- Electric fires. A 1-A extinguisher will put out a 20x20x20 wood crib of dry red oak. A 2-A will put out about twice what a 1-A does. The B rating: 10 -B will put out about 10 square feet of flamable liquids. C Electrical safe to use on energized electric fires. and will knock down the flames without zapping you. However if the unit is still engergized it will keep producing heat and probably flair up again.
If you are concerned about an engine comparment fire google the following for a good article on the subject. Detection of Fires in Heavy Duty (HD) Vehicles
I hope I've answered some of your questions. I suggest being very skeptical of any "new, innovative, groundbreaking" claims on any fire protection product. Fires have been around longer than man. Billions of dollars have been spent over the years trying to find new and innovative ways to control it when it grows beyond control. There are some amazing systems out there but they are very spendy and all require periodic maintenance.
Be smart, Be Safe, Safe Travels