>>>You have checked out Nativescript?
>
>100% agree with principle but concerned at the thin runtime layer. What's the performance hit?

From their docs 10%, probably reached by test cases they are already happy with ;-) I think the product is too new to benchmark now.

But I was more impressed with their solution offering all native APIs of each platform within a day via include generation program - if they have not wrapped different platform interfaces (or botched the job) you could do it yourself, similar to falling back to C sometimes in vfp for pointer fencing.