Are you building a mobile app with payments?

I'm looking for indie hackers building apps with payments to get a better understanding of how I'll do it for my own product.

What are you building?
Are you using in-app or out-of-app payments?
Do you have users in more than 1 country?
If so, how does your payment system work with fees, legal, taxes, etc.?
Subscription or one-time?