Sensor Tower - Sensor Tower is a platform for app store optimization and app industry intelligence.
Polls for WhatsApp - Create & share quick polls in your WhatsApp groups
App Annie - App Annie is a marketing analytics tool available for apps of all kinds. With App Annie, you can track sales, traffic, and a variety of other factors pertinent to monitoring an app's trajectory.
Curious Polls - Answer a question once a day for the chance to win £100/$100
appfigures - Cross-platform app store analytics for all of your mobile apps.
Twitter Polls - Polls embedded in tweets