Just like there is no single best medication or therapy for SMI, there is also no single best app. We can help you make more informed decisions in picking apps at the APA app evaluation website: https://www.psychiatry.org/psychiatrists/practice/mental-health-apps/app-evaluation-model.
If you are using any apps as part of care, it is important to let your care team know so they understand what you are using and can be aware. They can also help you check that the app you are using is safe and effective.