
Quirk is an open source, slimmed down CBT app for iOS. Unlike other apps, it doesn't force a particular condition on you. It doesn't assume that you're using it particularly for depression, which makes it useful for panic disorder, OCD, weight loss and more.
After one week, I really feel like this app is helping me let go of irrational ideas I tend to ruminate about. It has helped calm my constant monkey mind.