Making your java application respond to events when it's not in focus is hard. Hotkeys for java allows your application to register system wide hotkeys for this purpose.
Currently a windows verison is in development. A first release is planned for Early 2008 (Jan/Feb). A simple version of the library is in use in the Capturedit screen capture utility. Because of numerous requests to reuse this basic library this project was split off and slightly expanded on for it's first release (offering more than one key registration and more flexible modifiers.
If you are interested in assisting, contact the project admin.