With the Destiny Beta starting tomorrow, Bungie seems to be releasing the Destiny companion app a little early. This is probably being done to get you comfortable with the application.
The app is available right now in the iTunes and Google Play Stores. Users that have the Bungie mobile app can just update it and it'll turn into the Companion app.
The app lets you check out your inventory, but it also lets you check for messages from your friends and see tons of different stats. It also lets you check out some cool groups of players and forums so that you can keep up to date with all things Destiny.
Check out the links for the iOS version and the Android version below: