This is how Google Inbox and Google Spreadsheets works. See the slides from my recently produced GWT Create Session (<a href="http://t.co/ZvoaHxCoZT" rel="nofollow">http://t.co/ZvoaHxCoZT</a>). J2ObjC slide deck here (<a href="https://docs.google.com/presentation/d/1mW_Plm5jAygELf7qjVK7ZSIFjha0Q3TjOttX4x8oVWY/pub?start=false&loop=false&delayms=3000&slide=id.g6c99c794a_2_26" rel="nofollow">https://docs.google.com/presentation/d/1mW_Plm5jAygELf7qjVK7...</a>) Videos of the conference will be online soon.<p>Prior to that, some 20% Googlers also produced the PlayN library (<a href="https://github.com/threerings/playn" rel="nofollow">https://github.com/threerings/playn</a>) This was taken over by Michael Bayne who added an iOS backend by Bytecode -> IKVM -> Mono conversion. I beleive j2objc and RoboVM backends exist now as well.<p>The major benefit of the j2objc approach is the avoidance of GC in favor of ARC, the conversion of message-sends into C-method calls when possible, and integration with existing iOS toolchain.<p>When we started, it seemed like an iffy idea, but after developing a product delivered to millions of users on a high volume site (gmail) that has 70% code sharing, and being able to simultaneously develop, test, and deploy across the platforms reasonably efficiently, a lot of skeptics have become converts to the concept.