The aether goggles seem to be standard-issue equipment for Sharlayan Archons. Moenbryda had a pair, as did G'raha (they wore theirs around their necks). Krile has a pair, too, worn on her right arm, even though she doesn't seem to be an Archon, just a Student of Baldesion. So, I don't think they are particularly rare. As for whether they could be used to detect the tempered, no idea. No one seems to have thought to use the goggles that way, so maybe not? It could be that they only detect levels of ambient aether, but are not able to distinguish between normal and tainted aether.