I think that's a really interesting question to unpack. I have trouble separating my own skepticism about the technology from the issue of whether it should be mandatory. For example, a lot of these technologies, depending on the design and depending on which one it is, depend on the effectiveness of COVID-19 testing. If you're in a context where not everybody's being tested and it takes five days to get test results, then these apps are going to be minimally effective. They may be useful in some circumstances.
On May 29th, 2020. See this statement in context.