The problem with contact tracing apps is that their effectiveness has a quadratic relation with the adoption rate. They would be mostly useful to trace "random" contacts (since you tend to know which of your friends and family you saw within the last 2 weeks), but to be able to trace a possible infection both the infected and the "recipient" have to have the app and active. In Germany they said their 12M installs is "good" but that's just 15% of the population, so if you'd take a random pair the chance to detect a link is 0.15*0.15 = 2.25% ... so it's obvious that this isn't going to move the needle much. So in order for this to be effective, you need to have very high adoption rates, and it can only help in addition to other measures (wearing masks, hygene, avoiding indoor gatherings, ...)
I completely agree with you that this cannot possibly replace other measures such as masks, hygiene, and avoiding large indoor gatherings. Nor should it.
I think there is an additional confusion though. This is really an exposure notification app. If you used only this, and not traditional contact tracing, you would have to have a lot of adoption. But I think the general recommendation is to use both (1) these exposure notification applications and (2) traditional contact tracing by people trained to do it. Then you don't need as large an adoption to get utility. Traditional contact tracing can be effective, especially for people you know you contacted. But it is slow, and does not handle well the people you don't know. By combining them, there is a greater odd of notifying those who may be potentially infected. As long as you're also doing traditional contact tracing and other measures, a lower adoption rate for these applications can still be valuable.
Full disclosure, I work for the Linux Foundation. But I still believe this anyway :-).
The other problem is which people are likely to install the app. It basically requires a modern Android or iOS smartphone with internet connectivity, which probably excludes the really at-risk groups that are of most concern: https://www.dw.com/en/loved-or-loathed-how-germanys-coronavi...
So, elderly people are less likely to use a smartphone (though I suspect not THAT much less likely). But the people they come in contact with probably do use one, mostly. Generally these should work on any smartphone under five years old.
Trying to create hardware token for this. Because myself and many friends are not able to use this. And if I think of old people not able to handle smartphone, this should be useful.
https://github.com/Lurkars/esp-ena
