The biggest obstacle is likely that you need to be a licenses money transmitter in all major jurisdictions to carry out what you describe. The second you let a

The biggest obstacle is likely that you need to be a licenses money transmitter in all major jurisdictions to carry out what you describe. The second you let an American tip an Iranian there will be trouble somewhere. It's not an unsolvable problem but you probably need to limit the scope a bit. There's a lot of implementation details hiding behind "accessing the tips they've received". I believe Flattr started out limited to the SEPA area and slowly expanded from there.