Two good indicators of revealed preferences are things the people tend to value a lot: time and money. If you look at how they spend their time and how they spend their money, you can infer quite a lot about their real preferences.

If a measurement matters at all, it is because it must have some conceivable effect on decisions and behaviour. If we can't identify a decision that could be affected by a proposed measurement and how it could change those decisions, then the measurement simply has no value