MarketPress POS system integration

I'm wondering if anyone can tell me if MarketPress or any other eCommerce option can be integrated with a Point of Sale (POS) system. I've looked around and found this thread from a little over a year ago:

I'm wondering because I've got some friends looking for new ideas for plugins, but they don't use WPMU. If this functionality doesn't currently exist, they may be interested in making it.