Here's the whole in-person sales system that runs from my still-kicking first generation iPhone. It uses three apps that integrate together, even without the fancy features of iOS 4.
RingItUp Pro handles inventory and sales tracking.
CC Terminal handles credit card processing.
Print n Share does the printing.
First, I enter all of my inventory into RingItUp Pro. This lets me know on-the-fly how many of each item I have in backstock.
Then, when a customer makes a purchase, I enter a sale. If it's a credit card transaction, I enter their address into my contacts so it will be there to verify the credit card. If it's cash, I don't have to do that, but I do always try to enter people's email and get their permission to be added to my mailing list. I haven't started an email newsletter yet, but I will someday.
To process a credit card, I then click the credit card icon at the top of the screen. All of the details about the transaction and address info are sent over to CC Terminal.
One day I'll get a more modern device that can connect to a swiper, but for now I just enter the card number by hand.
After the charge is approved, it sends me back to RingItUp Pro and marks the sale as paid.
I then have two options, send an email to the customer or print a real receipt. When I choose Print App, it sends the receipt document to Print n Share.
And here's where it gets crazy, fancy, and robust. I've configured it to use a gmail-based print queue. This means that the document gets sent from Print n Share to a special gmail account.
On the computer, there's a software called WePrint that checks this account every few minutes. When a new printer document email arrives, it is downloaded and printed immediately.
This solution is robust because it doesn't depend on the computer being turned on with the print server running in order to initiate a print job. Since I use a notebook computer for everything, it's likely that I would forget some step of the morning setup. No big whoop. The document sits in that gmail account until it gets printed. I just turn on the computer, connect the printer, turn on the print server and poof! The document spits out as if nothing happened.
And here's the result: professional-looking sales receipts printed from an inventory tracking, credit card processing sales workflow that runs on my phone. Maybe I'm just getting old, but this technology seems miraculous to me.