Almost entirely useless. They'll just wait for it to dissipate.

Some people will accidentally set it off themself... it's bound to happen but when it will happen it will prevent the owner of the car from using his car for some time and ever prevent other people around to drive safely.

Just buy a cheap car that nobody like. They wont steal that.

Seems as if it would work--car thieves and robbers of convenient stores always seem rushed, as if they're in a bit of a hurry for some reason.

What's the name of the band in that video?

Nice touch with the Death from Above 1979 song.

But I'm not sure how a theif could set it off and the owner won't. Is it a matter of hitting the thing?

this is old news , my neigbours had this in their home office 15 years ago!
coupled with deafening siren its total sensory deprivation.
and as for waiting for it to dissipate , i think the smoke kept pumping for ages.

Yup, it works like a charm, the retail company i work for has them installed in every store. I've been in the store when they go off, it takes about 15 seconds for the air to be filled with a fog that prevents you from seeing so much as a foot in front of your face. It works very well if the theives don't know their way out thats for sure!