I resisted smartphones for some time.
I have finally relented. However, I treat it as if it were a CIA agent in my pocket, even when it's off.
The fact is that McAfee is right about surveillance, apps, and backdoors. I not only don't use it for online banking, I don't have a bank account. I don't only take care in what I communicate with it, I take care in communicating at all when it is present.
I know I am able to be tracked with it, even when it's off. I can be heard, seen, etc. I don't have free games, view porn, etc., because I have long known that if you don't pay for a service, you are the pay for the service.
It is a spy in my pocket, and were it not essential to have communications capacity, I wouldn't have it at all.