There are good solutions out there. I'm currently working for a startup that's doing iPad based POS.
Without trying to toot our horn, it's a lot better than any of the legacy systems out there.
So no, there ins't really a reason why there isn't a solution except that nobody has made one yet (except for us and a couple of other tablet based POS systems).
I don't know if this is kosher or not on HN (still relatively new to posting here), but what is your startup? I think that would be a space I am interested in and would love to learn more.
Without trying to toot our horn, it's a lot better than any of the legacy systems out there.
So no, there ins't really a reason why there isn't a solution except that nobody has made one yet (except for us and a couple of other tablet based POS systems).