Conversation-driven follow-up reminder app

Wanted to work on a small app idea over winter break but I keep hitting a roadblock. The premise of the app is to help people be more thoughtful by catching future-relevant emotional or logistical hooks in conversations (tests, trips, interviews, health issues, big decisions) and reminding you to follow up at the right time. There's been so many times where I personally get overwhelmed with other things in my life and forget to check up with those important to me so wanted to build this for myself. But iOS blocks iMessage access entirely. No reading messages, no streaming, no long-press actions, no sender context even on share. I want this to feel lightweight and low-friction for users. Anyone know any workarounds for this?