You shouldn't use a smartphone if you expect to be TAO. Even the hardware could be compromised. Use a laptop with Linux for anything anyone might want to track...
Then why is Moxie advertising with Snowden the Signal app as communication for TAO targets?
And for non-TAO targets, WhatsApp is just as good as Signal – the users won’t read the source code anyway, and in both cases President Trump gets your social graph.
Aka NSA's "we really need to get access to this device and will fund diverting backbone traffic / writing firmware malware / whatever else we need to in order to get it" team(s).