[soapdog]

Have you looked into the blackphone?

Also, mozilla does not make hardware, it can't provide you with the hardware safety you need.

Android is not open source. AOSP is open source but a lot of the stuff you see in a modern high-end Android device is not OSS. On the other hand, all of Firefox OS, its built-in apps and its associated services are FOSS. You can check the code and audit it.