With all of the existing productivity benefits and organization features in the Notion desktop app, Momentum would be a great addition to the integration/connection options for Notion users. The number of Notion users is increasing fast across the globe and this might also help increase the number of Momentum users. Although Notion is great for productivity and organization, it lacks any features for time management and focus modes. Momentum would be the app to cover that for Notion.
I would pay to upgrade to plus if I could use it with Notion. Notion users are dedicated because of the amount of effort we have gone given to set up our perfect templates, etc. Like Mytia said, what it lacks is something to help focus on the task at hand, as Notion is quite overwhelming by its nature. Perfect marriage to be honest!
Got plus, pease integrate Notion ASAP