I've never had the need to use one, or even considered one, but given that we sit on a very hot carrier of flammable liquids, I can certainly see your logic.
For fires caused by faulty/badly placed cookers, then maybe. But I think most people exercise good camping sense and would place cookers in safe locations.
In any case, if you were to carry such a thing with you, then why not a simple kitchen type device that you can buy in most hardware stores ? I found this on B&Q's website:
http://www.diy.com/nav/fix/safety-se...skuId=12979285
A fire blanket might be more useful I think, doesn't run out and not as messy!