The Apple Store offers the Square Credit Card Reader for Apple iPod touch, iPhone, or iPad for $9.95 plus $4 for shipping. It allows you to accept credit cards via the free app from the App Store, track sales, tips, and tax, and send receipts electronically. (You're charged 2.75% per transaction with any approved credit card, including U.S.-issued Visa, MasterCard, American Express, and Discover cards). See the product page's "compatibility" tab for a table of compatible Apple devices.

This item — and dozens more — can be found on our Apple Store 2013 Back to School Sale page. Also, be sure to check out all of our featured merchants on the dealnews Back to School Sales micro-site.