If you're going to monitor every aspect of a person's life, you're going to generate so much data that you'll generate almost nothing but false positives. None

If you're going to monitor every aspect of a person's life, you're going to generate so much data that you'll generate almost nothing but false positives. None the less, I don't see why you couldn't just scale your level of significance way up and be a useful screening device. Obviously any diagnosis must be made by a doctor, but that doesn't mean your biometric information wouldn't be useful.