Ask HN: Cross-platform, rich client app in 2013?

With tablets taking off the way they are, having a client (for a client-server app) that runs on a tablet is becoming higher and higher priority. Running on desktops is still required too. What is the best technology today? Flash and Silverlight are out. HTML5/Javascript? Ehhh, not sure -- I really like strongly typed languages and a compiler to catch my mistakes. Something like Xamarin? Anything else?