Narrow - Narrow helps you build a targeted audience and increase your influence on twitter.

Quantcast Measure - Quantcast Measure provides free cross-platform audience measurement for a mobile app, website, network or platform.

Follow3rs - Follow3rs enables you to add more followers to your Twitter account and become prominent in no time at all.

Affinio - Affinio is an advanced marketing intelligence platform that leverages the interest graph to understand today’s consumers.

Followerion - Followerion is the most trusted site regarding how to get more followers on twitter.

Talkwalker - Talkwalker Consumer Intelligence Platform: built for speed of insight, ease of use, and data democratization