[midoridensha]

I think geo-locking is definitely a workable solution. Add a cheap GPS receiver and the machine can tell where it's located. Then if it's moved between countries, it can refuse to work until the user pays up. Since Apple controls the OS, they can bake this in: bring up a web browser page pointed to a payment form, linked to their Apple account.

I don't see why this wouldn't work. It's not like Apple users are going to rebel and refuse to buy Apple products because of something like this.