The compatible MOBI app version with iOS8 will be V 6.0.9. We have already uploaded the new patch (v 6.0.9) to AppStore and should be available for download soon.
If you have upgraded your device to iOS8, you might face few UI issues and abnormal exit of application on some specific workflows. We have fixed these issues in the next patch version 6.0.9
If you are using older version of MOBI app (like version 5.x or even 6.0.8) built using SDK, we recommend you to download the latest SDK package (version 6.0.9) from Service Market Place (SMP) and rebuild the app before moving to iOS8. SDK package will be available for download from SMP once app is live in iTunes.Please continue to use XCode 5.x to build the application. Compilation using XCode 6.x is not yet supported and application may exhibit user interface issues.
Feel free to reach out to me if you have further questions