I was able to create a mobile app for Tiller with AppSheet. No coding is required, but there is a somewhat tough learning curve to learn how to setup the Tiller Data so that appsheet can use it. You can demo the app here (you might need to resize your browser to be similar to the aspect ratio of a phone). You can see how I setup the Tiller Data to work with AppSheet here.
I was able to get the app to: show balance histories as graphs or a table, see and edit all transactions, see only new uncategorized transactions (and categorize them), track your monthly budget to see how much is left in a given category, see account balances etc. I’m sure anyone with some time could figure out more. For a couple of the displays I needed to create an intermediate sheet to get appsheet to import the data correctly.