How It WorksYou install Between on your Apple or Android device and provide the mobile number of the person you want to use the app with. Most use the app, which is free, with someone they are romantically involved with, though that's not required. Once the request is accepted, the two can use instant messaging, keep journals, exchange voice messages, post pictures and leave comments. Between also offers a blog-like space where the two users can create photo albums and long notes. Pictures can be tagged to a "Memory Box," which arranges them in a stream of tiles. Reminders for anniversaries, birthdays or any special days such as the day the couple first met can be set in the app's calendar. The content created is private to the two users and the app can be password protected.