My phone is littered with apps like these, which seem well designed to address a very specific problem which I don't have very often. The problem is remembering the app's there 3 or 6 or 9 or 18 months later when it would actually be useful to me.
I always think that the goal of apps like these is build userbase and then get acquired, like darksky or waze: the big providers realise they have missed a trick and then it becomes the default.