Rhomobile is an open source mobile application development platform that allows developers to write applications once and deploy them across multiple mobile platforms. Key features include: - The Rhodes microframework for building locally executing, natively optimized mobile apps using HTML, CSS, and Ruby. - RhoSync for synchronizing data between mobile apps and web services or application backends. - Tools like RhoGen and RhoVer to generate, build, test and distribute mobile apps. - Support for building rich client apps that work offline using local databases and work well on smartphones. Apps can be written once and deployed across platforms like iPhone, Android, Blackberry.