unwelch - Web app for friendly betting

Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.

Finger Tap Challenge - Finger Tap Challenge is a simple challenge game that involves two players who will have to tap on the screen as fast as they can to win the challenge from the opponent.

UserTest.io - User testing made simple. High-quality, affordable user testing solutions from real users, here in the UK. Improve your usability!

Spinnner - Challenge your friends to a spin-off (literally)

UserTesting.com - Usability testing has never been easier. Get videos of real people speaking their thoughts as they use websites, mobile apps, prototypes and more!