Midnight Coders announced support for Grails with version 4.1 of WebORB for Java. The documentation for the Grails integration is now ready, which includes a tutorial for a basic remoting application and a screencast showing Grails integration with a Flex application. Now as you may already know, Flex can run as an AIR application on the desktop and on several mobile devices, which makes it very easy to connect a Grails application to multiple client types.
Here is a link to the new documentation, examples and screencast:
http://blog.themidnightcoders.com/index.php/2011/04/28/weborb-and-grails-integration/