I use take-your-pill
Not released on any store and near as in I can tell has no telemetry.
Not sure about at rest encryption, but I just label my pill with the first letter or two.
Pretty old project, but it's pretty well done and doesn't need a whole lot of the "new" features.
I like that I can keep getting reminded as I don't always take it right when I need to.
It's a pretty simple interface.