FSK between Arduino and iPhone/Android

Hello everyone! I have been having issues trying to get this going. I want to make a small arduino that connects via headphone jack to an iPhone/Android. The goal is to print a 16 digit s/n from a reader to the phone. I only need 1 way communication going from Arduino -> phone.

I have an Arduino Uno, Arduino pro 3.3v, and modem adapter. You can find that adapter here:


I already have the code to read a s/n. Now I just need to find a way to print it via softmodem to an external device. If someone could help that would be great!

thanks for your time.