While, sorry, it's not an app, my brothers and sisters started a sibling group text thread after my mom's first hospitalization. I had the first assignment and stayed with her 24/7 when she was released from the hospital. I texted daily updates on the group text to keep everyone in the loop, particularly my SIL who relieved me.
We had apple phones and use (1) group text (2) shared calendar for medical appt (3) shared notes for groceries lists, to do lists, questions for doctors , medication lists . These work wonderfully for us
Your phone has an app. You can set up your group right on your messaging app. What's app and Facebook messaging as well. Or you can set up a private group on FB and only invite certain people. ZOOM allows about 30 minutes for free that one person can set up on a schedule
https://www.youtube.com/watch?v=Pwa0NyPQPBw
Or,
https://www.aplaceformom.com/caregiver-resources/articles/family-caregiver-apps
Or browser search "scheduling app for caregivers"
connected caregiver
verified care
I just downloaded both to see which one I like.
It is free for 10 users or less and it is very customizable.
Disclaimer: Not an advertisement.