Jasonette is an open source framework that allows you to build native apps using a declarative JSON based syntax from Jason.
With Jasonette you can build apps very quickly and there are several great examples included such as a tutorial app featuring many off the available features, a Twitter app, and an Instagram app. Entire Apps can be loaded over HTTP so your entire app can be stored in the cloud.
Jasonette is fully extendable so you can add any feature you like, and you can place Jasonette within your existing code if you only want to use it for part of your project.
This video introduces Jasonette:
You can find Jasonette on the homepage here.
A nice framework for quickly developing apps.