number of days since last expense of a category, to keep in check against bad spending habits
For example, lately I have been going too much at fast food drive-ins and I want to be able to remember when was the last time I indulged in this unhealthy habit. So when I feel like I want to get myself junk food, I can see in the app that last record dates back from...
this can work for any kind of "guilty" expense that we want to keep under control, if not remove entirely.
I could do it in a "days since" app, there are many, but this is something related not only to a bad habit but a waste of money, so it makes sense to me to want it integrated into my finance app and not into some food diary app, which I don't have and do not intend to use.