Rhodes

Rhodes (http://rhomobile.com/) is similar to PhoneGap insofar as you develop an Android application whose user interface is defined via HTML, CSS, and JavaScript. The difference is that Rhodes bakes in a full Ruby environment, with a Rails-esque framework. Your Ruby code generates HTML and such to be “served” to an activity via a WebView widget, much like a server-side Ruby web app would generate HTML to be served to a stand-alone web browser.

Similar to PhoneGap, you can either build the project on your development machine or use their hosted build process, RhoHub. The latter method is recommended, partly because the requirements for local builds are higher than those for PhoneGap—notably, Rhodes requires the Native Development Kit (NDK) for building and linking the Ruby interpreter to your application.