Disclaimer: I'm Matt, the other half of Iconoclast Labs.
That platform limitation of RubyMotion and the cross-platform nature of PhoneGap is acknowledged multiple times in the post.
From a business perspective, the cross platform nature of PhoneGap may make it a better choice for some projects but from our short comparison of the PhoneGap version of the app deployed on both platforms, iOS appears more promising* so that's why we chose to write a native version for iOS (plus, coming from more of a Ruby/web background and having no Obj-C experience, RubyMotion lowered the barrier to entry for that). It's been an interesting learning experience for sure.
I'm honestly not sure, I have no experience with Objective-C but just from reading I think you'll still need to write an Objective-C interface/wrapper for your C code before it can be interfaced with RubyMotion.
That platform limitation of RubyMotion and the cross-platform nature of PhoneGap is acknowledged multiple times in the post.
From a business perspective, the cross platform nature of PhoneGap may make it a better choice for some projects but from our short comparison of the PhoneGap version of the app deployed on both platforms, iOS appears more promising* so that's why we chose to write a native version for iOS (plus, coming from more of a Ruby/web background and having no Obj-C experience, RubyMotion lowered the barrier to entry for that). It's been an interesting learning experience for sure.
[*] http://iconoclastlabs.com/cms/blog/posts/chatoms-app-store-e...