The Bar Tab is a great concept and would solve a big issue by eliminating a roladex box full of credit cards stored on the back counter of most bars that allow customers to open a tab. However the app should communicate and post in orders. If you pre auth a card for $50, you should be able to place order items or apply that amount to an order. What would be really nice if the pre auth amount would show an updated balance as more items were placed against the open order so the wait staff could see when a customer was getting close to the pre authorized amount. Also it would really useful if the card holder would sign up front like when I check in at a Sheraton, I insert a chip card, sign the Ingenico ISC250 for incidentals on the room. That way if the customer walks out of the bar and cancels their card without closing their tab the merchant doesn't have to worry about chargebacks since they presigned earlier. At minimum the Bar Tab app should be able to posted to an order.