I came across Topify which notifies you via email when someone follows you or direct messages you through Twitter. The email notification provides some nice insight into those that start to follow you.
Topify lets you know if you are already following that Twit. If not, you just hit the reply button in your email application and you start to instantly follow that person. The Topify email notification also provides you with the Twit's Following to Follower ratio (a signal used to see how influential that person is). The notification also pulls in the data from Mr.Tweet. Mr. Tweet's data shows how engaging the person is and how many recommendations they have (another signal for influence).
In addition, the notification provides the ability to quickly block the person, unfollow them, or even report them to @spam directly from the email. I find this service very useful as it alerts me to new Twits that are worth the follow (or the block). I recommend signing up this service. It is currently in beta, but they are pretty quick in providing an account.