1. Mindshift (Android and iPhone) - is designed for teenagers and young adults who want help with feelings of anxiety. The language and interface is simple, it provides some useful information about what anxiety is and helpful strategies to try and tackle it. There is also a nice quick tips section for use in panicky situations. And it's useful for adults too.
2. My Mood Tracker (iPhone) - Keeping track of how we feel helps us notice that sad moods do indeed pass, and can also potentially helps us link our mood to things we do, places we go and people we talk to. My Mood Tracker can collect additional information on sleep patterns, exercise and a whole caboodle of other things.