Apple wants you to use their 30 pin interface, but that requires going through their MFi program and that lets them control the hardware ecosystem like they do the software ecosystem.
To be fair, there are certain advantages to hardware manufacturers willing to jump those hurdles. You're able to ensure no one can make software for your hardware, for one. Secondly users who plug in your hardware can automatically be taken to the app store to download your software.
Also the headphone jack is available on all phones and if you develop for 30 pin interface, you have to design different hardware connector for different phones
Is there anyplace online people in the MFi program hang out (forums, usenet, mail lists, etc.)? I've got some very basic questions about the whole process, but it seems like such a black hole (from the outside looking in).
It would be great to use the ipods or ipads for industrial data collection, but we'll need IR and a way to get data on/off without network connectivity.
To be fair, there are certain advantages to hardware manufacturers willing to jump those hurdles. You're able to ensure no one can make software for your hardware, for one. Secondly users who plug in your hardware can automatically be taken to the app store to download your software.