When I was in high school, I used to mow my neighbors' lawns to make money in the Summertime.  One of my neighbors had an apple tree in her backyard; ans eh told me one how much she loved it, but hated the flies it brought into her house.  Next time I see her, I'll have to ask her if she's tried this...

Luckily, my wife and I have never had a fruit fly problem, but house flies love our place in the Summertime.  Maybe something similar would get rid of them, too.  Anyway, check out this clever fruit fly trap!