Comment Re:How does Square do it? (Score 1) 96
It's actually pretty different -- square is a simpler, passive device that essentially uses the mic and a tape head (remember those!) to read out the magnetic stripe on the card.
This is actually much more sophisticated, since it harvests enough power from the audio signal to power simple sensors and a microcontroller, as well as giving you two-way communication. Also, it's not iphone-specific -- there are billions of cheap devices that you can now target with the same hardware; from this point of view the advantages are similar to the square.