Just seen a post about this application at LifeHacker.
Thinking Rock is a cross platform GTD Application for collecting and processing your thoughts using the GTD Methodology.
Thinking Rock allows you to collect your thoughts and process them into actions, projects, information or future possibilities. Actions can be done by you, delegated to someone else or scheduled for a particular date. Projects can be organised with ordered actions and sub-projects. You can review all of your actions, projects and other information quickly and easily to see what you need to do or to choose what you want to do at a particular time.
I am going to check it out and then add it to my review list for this site.