I think :
1) It is of course possible " in theory";) . The iPhone can stream the microphone audio into the HA with no problem
Try: "Setting" -> "Accessibility" -> "Hearing Aids" -> "Resound Linx" -> "Start Live Listen"
2) However, you can not do that with the line-in audio. I am wondering if this is done to force you to buy the separate $289 (check amazon ) device called "ReSound Unite Mini Microphone" http://www.resound.com/en-US/hearing-aids/accessories/mini-microphone That Resounds Web page says, "Want to hear music while exercising or mowing the lawn? Just plug the Mini Microphone into an MP4 player and stream sweet music directly to your hearing aids."
3) The feature we are speaking about is crucial. The main problem (for me ) is not lack of music during the mowing of the lawn.
The main problem, I struggle !!! to use the regular business corded phone at work.
The solution should be simple:
1) Connect the iPhone with the desktop phone using the existent "headset" jack and use the the iPhone microphone to speak and your HA to listen to.
It requires no extra hardware, Just one (or two) extra line of the software code might have resolved the issue.
2) Connect the desktop phone using the existent "headset" jack with the dedicated Bluetooth adapter to use you iPhone with HA connected wireless
I already $7000 for the pair of Linx 9 devices. I do not believe this can not cover the extra simple addition to the iPhone software .
Alas neither solution is available.
Apple, are you listening to: we NEED !!! this feature . Please support me.