How do I send and recieve SelfieCheckr messages?

If you send someone a SelfieCheckr message, they can't see the content unless they send a Selfie straight back. Then, your content is displayed and Selfie-Check captures their instant reaction. The same applies if you receive a SelfieCheckr note from someone else - you must first take a Selfie in order to view the content, and then the camera takes a second photo to capture your reaction.