If you have flies in the area of your flytraps, you shouldn't need to catch anything. The flytraps will do their thing and catch them themselves eventually. Unless you really just love running around chasing after flies. Just have patience and wait til the flies are attracted to the traps. The other day I was cleaning up my plants and saw three flies get caught within about 1/2 an hour. But its not like you put a flytrap out and immediately flies are all over it and the traps are snapping shut. It takes a while for the right conditions to happen. I see flies crawl in and out of traps all the time and never get caught.
If you are trying to get rid of a lot of flies, it will be slow going unless you want to get a lot of VFTs. Once they eat a fly/bug it takes a while (days) for it to digest it....then reopen and catch another one. And it will only do that a few times before the traps wears out naturally and dies.
I don't know about a VFT for pest control but they sure make great plants to have.