Usually Twitter users can know if another person started following them by just taking a look at their profile. But Crowdfire makes looking for the opposite just as easy, sending you a notification each time an account stops following you. Whether you want to return that unfollow is a matter of personal preference, but at least you'll know.
Other interesting feature is that Crowdfire lets you search for Twitter users who are inactive or send private messages automatically to your followers. The first of these features lets you know who hasn't tweeted anything for one, three, or six months.
Crowdfire is a very interesting complement for these two social networks; it not only lets you know who unfollows you, but it also offers other useful tools. The only problem with the application is that it can be somewhat unstable on certain devices