IPhone is closed source and any kind of rootkit can be installed by 
    Apple/NSA secret court system. I suggest not using a smartphone if you are 
    serious about security.

I absolutely disagree. While you are correct that in theory an iPhone can have rootkits and other backdoors installed on it by the NSA, in practice, I've found that the average user's computer can be compromised far more easily than their smartphone. Remember, we're not dealing with security professionals. We're not even dealing with people who can use PGP to secure their e-mail. We're dealing with rank newbies. In such a situation, it's far better for them to take incremental steps today to secure themselves (e.g. by using Signal to communicate, rather than e-mail) than it is for them to spend a year learning about encryption and having PGP key signing parties before they can set up a secure infrastructure.

Comments like these are why I have a deep frustration with the "security community". It's letting the perfect be the enemy of the good.