App served by Flask running on App Engine. Data persisted to Firebase. Costs me approximately $0 per month. 100% uptime afaik.
Yes I use CrushEntropy for planning my day and tracking how I spend time through the day (a column of plans next to a column of actual gives you a good sense of how things are going), and Google Calendar for all meetings.
I plan to add some selective syncing with Google Calendar. I haven't had a pressing need for it though. Do you need that?
None of my personal projects get used much so none of the costs of Firebase really come into play for me.
I sometimes use Flask for the same thing but I end up having to write my own HTML and CSS and routes and... Rails just takes care of all of that. I find it faster by a huge margin.