> I think the problem is, what good does it do if someone has some predilection toward suicide but isn't aware of it? If they were going to be resistant to addressing it without this tool, why would they be less resistant to it with it?

(Not a researcher in this area, but someone who's dealt with depression) this is a big concern of mine, and it doesn't seem different from the issues with a standard lie detector. A depressed person can feel fine one day and not the next. If we think of things like anhedonia, grief, guilt, etc they aren't constant day to day. A lot of suicides are preventable simply by getting a person through a day or two. This is the number one reason I'd argue for waiting periods on pistols (most gun deaths are suicides btw). Would such an event even show up on this device? Timing becomes an extremely important factor here. My understanding too is that we still don't even know how these diseases function from a chemical level in the brain (norepinephrine, dopamine, and serotonin). Categorically there can be: too much, not enough, broken uptake mechanism; and our main treatments are with reuptake inhibitors (SSRIs or SSNRIs) and these tools are really limited in those categories (which are very high level fwiw and need to be broken down substantially more to target good drug delivery).

I am also very concerned about how this technology can be abused. While I agree that there can be a lot of uses to it, that doesn't mean we shouldn't be concerned with how it can be abused.