There is an element of legitimate use where privacy is not abused like a baby monitor or tracking a child's location. Even so, these products rely on and exploit our fears under the best of conditions. I have certainly thought that it would be nice to have a locator on a 10 yr old that has gone off for a bike ride but it is all wrong. If I need one of these things then there is something else that needs fixing.
It is the same for matters of trust between adults. I don't think that you can betray a trust in order to verify that it is well placed. If you need to spy on someone then there is no trust to begin with.
The amount that we trust others is a good measure of our own trustworthiness. I don't see how using this kind of tech is any different than looking through someone's bedroom window. It is perverse and makes the world a less comfortable place.