Sounds reasonable enough. I've seen the idea a couple of times in hydroponics books, but I've not had a chance to try it myself as all of my tomato plants are outside. May need to though--I've not seen an single bee all year...

For one plant its easy enough to just use an electric toothbrush. If I had multiple plants, I'd just give them all a shake 2 or 3 times a day.
While a reasonable idea, it seems unnecessary and likely to blow pollen all over the place.
Hope you don't have allergies.

azee_2009
I'm not sure how many tomato plants you plan, but placing a fan underneath each one seems unreasonable to me for various reasons. For just a couple of plants shaking them daily, or using a electric toothbrush on the back of the flower clusters typically work well. For more plants or people that don't want to do the labor, placing a few oscillating fans around the room works great. The fan direction isn't important, air circulation is. For the truly lazy, the oscillating fans can be on timers. But typically are set to run 24/7. The constant air circulation helps prevent fungal disease as well (especially in humid greenhouse conditions).

Walk through the greenhouse once every two days in the afternoon with a leaf blower at low speed. Quick and very effective...

The hydroponic store in my neighborhood, just puts an osculating fan near the plants and their plants have tons of fruit. As homehydro said, I dont think the direction of the fan really matters.