[fluoridation]

I don't think that's quite right. It's not that they mildly want to cancel some plan, but rather that they don't really want to do it and are only going along with it because they think the other person wants to do it. Thus the hypothetical app would solve the situation where both people are doing something only because each thinks the other person wants to do it, but in fact neither wants to do it and neither wants to disappoint the other one by telling them they don't want to do it.