Square Credit Card Reader
What it is: The Square Credit Card Reader offers a simple way to scan credit cards with your iPhone, iPod Touch or iPad.
Why it's awesome: Great for small businesses, the reader plugs into your iPhone's 3.5mm jack; after you download Square's free app, you can start accepting credit cards on the go. When you place charges on the reader, however, remember that Square charges a fee of 2.75% per transaction.
Where to buy: Apple