A [wet-bulb temperature] reading of 35 °C (95 °F) – equivalent to a heat index of 71 °C (160 °F) – is considered the theoretical human survivability limit for up to six hours of exposure.
If you are on android or ios the phone already cryptografically verifies that the operating system has not been tampered with on a hardware level. Since the operating system is then "trusted" it can verify anything you do on it
Android is ahead in most other countries. 70% worldwide