Sproutapp was a secure mobile platform that used its artifical intelligence engine to allow users to send anonymous messages to people they know, which is only received if it achieves a certain positive threshold.
It allowed people without the application to recieve the anonymous message as an SMS, prompting them to install the application and reply or send their own anonymous message.
Unfortunately, whilst the app worked well, introducing users onto the application was difficult. In addition, the AI behind analyzing the "quality" of the messages was a beta implementation that had teething problems, stunting the initial growth of the application.