How about we be given the option of audits…?
Peoples' lives depend on these devices working as advertised, how about making the firmware sources and related documentation for how these devices work open so that the end users can (or can pay someone they trust to) review?
The devices are likely built on patented technology which covers the hardware and algorithms, and copyright will cover the firmware as implemented.
I'm not asking for the devices to be made "open source" … for good reasons, the devices should expect firmware updates to be cryptographically signed. An outsider should be able to take your sources, build them, and come up with a firmware binary image that can be compared with the official one for similarities.