I think it is... I've been looking into integrating with toast https://doc.toasttab.com/doc/devguide/apiCreatingAnOrderWithPaymentInformation.html They have a way to mark orders as paid so you really just need a way to show a lighting invoice qr code to the customer. Like you said they do this for self checkout at the burger place. I was thinking you could have some tablet or similar to allow them to pay and as soon as the invoice is paid the restaurants lighting node can mark the check paid via their api