Cross Platform Mobile App Development

There's some new alternative for near native performance out there today:

1. Flutter Beta1 (Dart),
   pros: developed by Google, hot reload
   cons: the Dart programming language have a bit awkward syntax, standard library a bit incomplete compared to other programming languages
2. NativeScript Vue or Vue-Native (Javascript)
   pros: no angular :3, Javascript!
   cons: Javascript! very early
3. GoMatcha (Go)
   pros: Go!
   cons: very early

Sorry but i didn't intend to add ReactNative, personal reason: the error message is too freakin ugly. Also there are some others like Unity3D (for games, inefficient =battery-drain if you use it for static UIs), Xamarin (.NET), Scade (Swift), CodenameOne (Java), Kotlin/Native (Kotlin), Qt (C++), LiveCode (Transcript) and others (especially game engines like: Marmalade with C++/Lua, Corona with Lua) and of course you can choose other Hybrid or HTML5-based ones.

Update 2019-05-07: https://wails.app/ (not native, it's Golang + Javascript)
Update 2020-01-22: SvelteNative, FuseOpen
Update 2020-01-29: UnoPlatform