Baseband processors already operate independently with its own operating system and often have greater access than the application processor. Simple firmware update is all it takes right now to have it not turn itself off. CIA actively uses this capability on select targets, as per Snowden leaks, even when the phone is “off.”
Cellular modem that stays enabled despite user "disabling" will indicate itself by a quickly draining battery. Airplane mode and sleep data have much different battery consumption profiles. Indian people are not that stupid, and this will lead to a violent protest unlike China.
You don’t need much battery for tracking. Airplane mode is observable because it disables background applications as a side effect. If you only have one optimized spying application, this effect is no longer there. Only security researchers will be able to determine if the phone is really off. And let’s not forget that people need to make calls, no one’s carrying phones in airplane mode.
It will only take few more compromises in the name of safety & security to make this scenario all but reality. We’re living on the precipice of dystopia, and every crisis is a stepping stone.
