I work in this space and there are providers who don’t require proprietary client devices (bring-your-own-iPad) but there is still proprietary hardware in the form of a small box (think MiniPC) that runs locally at the store so the iPads can still work while the location is offline (this happens far more often than I ever would’ve guessed).

Most POS systems, even if they let you use your own iPads, will still require hardware for taking credit card payments and printing receipts.

Thanks. It's a shame someone can't figure this out without requiring any specialized hardware. iPhones include tap-to-pay, don't they?

Yes iPhones have tap to pay but iPads do not, they need external hardware. Even if iPads had this capability it won't work for some cards (no tap support, or that card is broken) so you will still need external hardware.

Also if you want an iPad-only setup then you probably have to have a 100% up network connection. This is harder to accomplish than you might imagine. There is a big reason why most POS have some kind of on-site server (or one of the POS units acts as the "brain" role), it's to centralize logic and also queue up data (like offline payments). I've seen a company do it with only iPads and 1 iPad acted as the "main node" but it did not work great in practice. iPads are much better at clients than they are servers (shocker).

I believe the contracts POS companies sign with VISA, MasterCard, and many others require the certify their hardware.

So I do not expect to see hardware agnostic POS providers.

I would love to be proven wrong.

Do they currently have a merchant account, or are they relying entirely on third party services?

It sounds like it's bundled. I'm guessing having your own merchant account gives you better options?