The problems of privacy and digital exclusion make this idea shit

Ths is the idea of using the opportunity of smartphones to do population
and individual-level research into menta,l health using the current
outernet.

Basically lots of people can't afford a smart phone nor internet access.
Too many people don't use electronic communication. Some don't even use
telephones or mobile phones. Some because they don't know how to use
them and some because they know how to use them but don't want to.

Thre's the whole privacy issue thing too. What many people don't realise
is that when they sign up to use a service like Facebook they're often
giving away their privacy rights already. The government also has
systems and ways to monitor electronic traffic.