Knowing when mom last used her phone?

I'm working on a simple tool to tell when my mom last used her phone (kind of like last active in some chat apps).

My mom recently got very sick. She lives about 20 minutes away, but she's active (as she can be) and some days I call or text to check-in on her and don't hear from her for hours (stressful). In these cases I just want to know if she's used her phone that day.

Maybe I'm just being paranoid, but I'm wondering if others have the same problem? What do you do?