Squareup.com

Take a look at this new technology for the iPhone, iPad and Android.  Squareup.com.  It looks to me like a nifty solution to enable users to easily accept payments on the road.  It can accept cash or cards as long as you have an audio input jack.  And they'll even send you a card reader and a sticker (for verification purposes) when you sign up.  Receipts can now be sent directly to your email or phone.  When you buy, it sends a photograph so the salesperson can check that you are who you say you are.  Your buyers are even encouraged to tip easily (with the help of a calculator that allows them to tip by percentage, even though they can still choose to tip by dollar amount.)  The keyed in rate is 3.5% +.15 and the swiped rate is 2.75% + .15.  Since, unlike similar companies,  setup and cardreader are free, there seems to be little to lose.