The idea that someone would have to buy a hardware wallet to be safe, but first audit the hardware and software is both a but ridiculous and infeasible. Unless one can actually inspect the code running on the device, auditing am open source library online doesn't tell you what is running on your device.
Maybe the sim card is on a timer to broadcast your keys after a year, so you just can't detect cellular signal usage now.
To securely own bitcoin you have to first create a new chip fabrication plant to then make your own hardware wallet.