Good, not great – Twigo - Manage Twitter Accounts - Track Twitter Followers and Unfollowers - Gain Followers & Find Your Audience Review

If you just want to see who's not following you back, this will work, though it's not the easiest to navigate. Don't use the feature to find new followers, because almost all it finds are bots that don't even post in English!
Review by kyvan81 on Twigo - Manage Twitter Accounts - Track Twitter Followers and Unfollowers - Gain Followers & Find Your Audience.