>I thought medical hardware had to go through stringent approval processes with health authorities?

Yeah this is the case. You have to have a phone from a list of approved devices which is not very long.

In fairness, diabetics should be carrying standalone blood glucose monitors as a backup. You never know what could happen to your phone.

As far as I know there is no general method of resisting electronic interference?

People already die of diabetes due to not having enough money.

Your proposed law would increase the price of treatment and lead to more deaths.

People who use such a feature would surely have a backup strategy in case their phone dies, the battery dies, is stolen, is lost, or is unavailable for any number of reasons (fucked up OTA update? hacked? some dumb app crashing their device?), right? If they don't and just rely on that single consumer-grade device working all the time, I feel sorry for them.

This glucose monitor excuse gets trotted out for these topics every time, but someone wielding a Flipper is probably the least of your concerns if device and connectivity reliability is so critical.