This will certainly work well but it is not a pure gasesous system. It looks like it uses c02 as a propelant and AFFF mixed with water as the extinguisher.
AFFF is very effective as a extinguishing agent because it interferes with the flame front between gasoline and the air. However because of its water content its not safe for sensitive electrical systems and it will leave a residue although not nearly as bad as dry chemical systems.
Pure c02 systems will work, co2 works by displacing oxygen, and cooling the flame no oxygen= no fire. However this is less effecive than halon. In a closed engine bay this should be a non issue though. C02 will rapidly displace all the oxygen and is the most effective in enclosed spaces.
If you want to remain completely damage and cleanup free halon is the way to go.
Halon displaces are and chemically reacts to interfere with a flame front. After it is done doing its work it dissapates into the atmosphere leaving nothing for cleanup.
Halon is hard to find now because it was banned by the Montreal Protocol because it depletes the ozone layer. It is relatively non-toxic, although you really do want to limit exposure.
Alternatively there are new halon substitutes which are fluorocarbons. These you may see marketed as halon.
Heres a little article I found for you.
http://www.nsxprime.com/FAQ/Accessories/fireextinguishers.htm