Groupon has announced the launch of Groupon Payments, a new "payments service backed by a guarantee to be the lowest cost option for the company’s merchants to accept credit cards." For any merchant that runs a "deal" with Groupon in the United States, swiped transaction fees are 1.80% plus $0.15 (MasterCard, Visa and Discover) and 3.00% plus $0.15 (American Express). As a quick reference point, Square is at 2.75% for the same basic swipe transaction, PayPal Here is at 2.70%.
More details about Groupon Payments are available at http://www.GrouponWorks.com/Payments. The Groupon Merchants app can be downloaded for free from the iTunes App Store. No details were released about distribution of the audio jack dongle.