I have a suggestion .. why not make an android or an ios app, it would be a lot easier for developers and for server owners to keep up with the latest updates like who bought your plugin or to keep an eye on your watched threads or your watched resources because your not always able to open your laptop like when your outside . do you agree???
Inorder to create an ios app, you need xcode which runs on OSX. To add to that, I'm pretty certain @md_5 is passionate about doing all of his coding on ubuntu/some linux distro, not OSX. As for android, I couldn't care less. Lastly, what's wrong with the mobile site?
But you should've though about what efforts it will take from them in order for them to fullfill your wish.but maybe in the future .
Should make it for android as if you don't have a mac or hackintosh, you can't develop any apps for iOS. Another thing is, you need to pay 100 dollars for a license to get your app on iOS, on Android its just $25
Perhaps, this article http://djangostars.com/blog/app-development-cost-android-vs-ios/ could help you. Good luck!
Sure, a mobile app would be cool, but the site/Xenforo is very mobile friendly. I have a shortcut to the website to my home screen and it works great. Like others have said, Tapatalk is another option. I don't have any experience with it myself though.