Curious Polls - Answer a question once a day for the chance to win £100/$100

Unity Ads - Unity Ads allows to supplement the existing revenue strategy by allowing to monetize thr entire player base.

Polls for iMessage - Group Decisions Made Easy. Create polls, vote, and view the results directly in iMessage. The easiest way to make any group decision.

MoPub - MoPub is a mobile monetization platform that helps publishers drive more revenue from advertising and mobile transactions.

minipoll - Create simple shareable polls in seconds

Appodeal - Appodeal is a supply-side platform for mobile apps, that serves and protects publishers rather than advertisers.