The problem to be solved: There are a lot of places where people are supposed not to smoke, e.g. public transportation, McDonalds, cinemas, shopping malls, public toilets, etc. However, there are always smokers they are nuts and do not respect other people's right at all. They simply ignore the rules and keep smoking. For the time being, there is not much we (people don't like passive smoking or don't like the smell) can do. These few culprits smokers can also cause a lot of damages, e.g. fire.
The solution: Can some big chemical manufacturers invent some anti-smoke perfume which can be spread publicly. The perfume is as fragrant as other French perfume and does not cause harm to anyone. However, if anyone tries to smoke under the perfumed environment, the chemical will simply react with the dust and narcotine and cause the smoker nausea and unwell and force the smoker to stop smoking immediately. I think it is a great idea and is totally commercially viable because I am sure a lot of the airlines companies, shopping malls management, cinema operators etc. will buy this anti-smoking perfume.
Reward: More fresh air and more mutual respect