Hello,
Thanks for your post.
Since Apple removed the headphone jack on the iPhone 7 (And later), a direct line/headphone output is not possible. This does affect some of our devices. Fortunately, there is an official Apple adapter that resolves this issue. You can use the iPhone Lightning Dock to connect iRig. This dock has a headphone jack that you may use to monitor your input.
For more information, check out:
http://www.apple.com/shop/product/MGRM2 ... dock-whiteAnother option would be to upgrade to an iRig Keys I/O 25 or iRig Keys I/O 49. Both of these products include headphone outputs, as well as studio quality audio interfaces. This would allow for use without any adapters.
Check these out here:
https://www.ikmultimedia.com/irigkeysio/