@hiransarkar, essentially, any app running on iOS that has user’s permission can access contacts, reminders etc. So you can have Pythonista running on an iOS device be a server and share the data for with your app on Windows.
That is of course not an ”always on” solution. For that you could theoretically web scrape the web version of iCloud, but I do not think Apple has made it easy, and it might be against their terms of service.