i dont think tones are your normal dtmf tones though
CHECK OUT the program made by VERIFONE for Square. (Square is a reader for ipad/iphone that plugs into the ipad/pod slot and lets you take card-present transactions as long as you have a a valid checking account. It plugs into the ipad/phone HEADPHONE/MICROPHONE PORT!!
LONG STORY SHORT, VERIFONE WANTS SQUAREUP.COM OUT OF BUISINESS, so they made a skimming program.
Google yeilds many links, but if somebody has permanate hosting i will share the file.... THe actuall app (not the news article) needs to be loaded on a jail-broken device. It mimics square's app, but jsut saves t2date+signature