There are some places where a not-completely 90% transparent piece of glass might not raise too much suspicion, but it could be more difficult to retrofit with a more traditional "pinhole" style spycam.
Like the wall of a shower stall, which you would expect to be less than 100% transparent.
I do think this threat model is less likely, however.
What I think is more likely is a Minority Report style system where there are pervasive cameras everywhere, constantly scanning your face, etc.... Maybe not constantly scanning your retinas and identifying you that way, but facial recognition alone would be more than enough. Either way, once you're recognized, you could be easily tracked silently, or you could be called out publicly by a nearby display.
Like the wall of a shower stall, which you would expect to be less than 100% transparent.
I do think this threat model is less likely, however.
What I think is more likely is a Minority Report style system where there are pervasive cameras everywhere, constantly scanning your face, etc.... Maybe not constantly scanning your retinas and identifying you that way, but facial recognition alone would be more than enough. Either way, once you're recognized, you could be easily tracked silently, or you could be called out publicly by a nearby display.