"Botometer (formerly BotOrNot) checks the activity of a Twitter account and gives it a score based on how likely the account is to be a bot. Higher scores are more bot-like. Use of this service requires Twitter authentication and permissions."
"Welcome to fllwrs, the Twitter follower tracker. Would you like to see a record of who follows and unfollows you every day?
Would you like to get notified when someone unfollows you?
Use fllwrs to monitor changes in your Twitter followers over time and keep a history of followers that have been lost or added."
"Real-time Information Discovery and Delivery
Dataminr transforms the Twitter stream into actionable alerts, identifying the most relevant information in real-time for clients in Finance, News and the Public Sector."
"Followerwonk helps you explore and grow your social graph.
Dig deeper into Twitter analytics: Who are your followers? Where are they located? When do they tweet?"