I use this for my table saw (and also for pinballs). It has a magnetic base for the table saw:
https://www.amazon.com/Digital-Angle-Finder-TickTockTools-Inclinometer/dp/B07GH7Y5ZM/ref=sr_1_13
Here is a short article on phone level apps - Verdict, ok for general use, doesn't beat a real digital level though.
https://www.protoolreviews.com/news/level-app-can-pros-trust-smartphone/35102/