Digital health technology is promising for improving mental healthcare by enabling continuous monitoring of behaviour by smartphones and wearables, new paradigms for testing in virtual reality, and analysis of big data through machine learning for prediction models. This might advance prevention efforts, and contribute to diagnostics and treatment; however, high quality studies of clinical effects and applicability are needed before implementation. In this review, we summarize the current status of the field relevant for a Danish mental healthcare setting, and comment on challenges.