* Sensors.
Most definitely. Small, sensitive yet robust sensing equipment always attracts a lot of interest. There are so many applications where timely data are of the essence that this type of development pays itself.
* Parfum / preventing body odor
Smart perfumes/deodorants... Tricky. They would be quite complex, and people don't want to buy expensive gadgets which get rid of unpleasant smells. My deodorant costs about two-and-a-half dollar per bottle, and it works just peachy. (At least, my GF thinks so :-D.) The only application I can think of would be in small, enclosed areas, like space ships or submarines. Or in areas where water is exceedingly scarce or cold---deserts, poles. That would make it an 'outdoor' product for which you can charge a bit more. But it would still be rather exclusive.
* Insect /pest killer
Another perhaps. I think people would prefer 'natural' remedies against these. I think they are quite elegant in themselves, and impossible to beat in price. Only against really threatening large swarms (locusts!) would artificial help be useful.
* Cleaning floor.
You mean that people actually worry about the state of their floor... :-) ? No, I don't see a future for microbugs here. I do see a bright future for poor old underpaid immigrants doing the chores you loathe to do yourself because you insist on doing better things with your precious spare time. Or think you are above cleaning out the toilet or drain :-). (However, if there is a little something which does that for me---no more yuck in the drain resulting from hairs, soap and filth would be worth something to me.)
* Micro robot for surveilance, exploration etc.
Falls within the realm of sensing equipment, although I doubt whether you can create interesting devices which are 'micro' in size.
* Creating new Ozone layer, reducing air pollution.
With a single heavy boust of solar activity, the microbots would be completely devastated. I think we should keep our hands off of the ozone layer until we fully understand the dynamics of Earth itself. Contrary to many popular reports, we don't. This application has a high 'feel good' factor rather than a high 'scientifically sound' factor. Air pollution, and mostly of the urban kind, is a different matter, however. Intelligent filters which scrub the air at a small, but continuous rate using very little energy can seriously improve the local environment, and thus cause massive reductions in diseases affecting nose, throat and lungs.
* Medical applications. (surgery, drug dispenser etc)
Always a good application for small things. But microbots must be fully understood before they can be applied---humans are not fond of risking their lives on the premise of new technology. I think it will start with sensors again: think of sensors which monitor cholesterol-, glucose-, or hormone levels which then trigger a small localised supply of concentrated medicine. Swallowing pills is primitive by comparison. On the other hand, if the technology fails, you have a lot of deaths to cope with.
