I don't think that there is a service/site that removes fake followers, since it is hard to judge who is fake, and who is real. I suppose you may be able to tell by their reactions(or no reaction) to some tweet(s) that you make, although I'm not sure of this idea myself.
Some users already provided a services that can determine fake follower and can delete it on the first page. I think they judge fake followers if the account is inactive and a few of activities in their profile. Fake followers is just a product of auto follow services.