title: gwt widget - mutually-exclusive toggle button
body: <p>I want a hybrid of a <a href="http://google-web-toolkit.googlecode.com/svn/javadoc/1.6/com/google/gwt/user/client/ui/ToggleButton.html" rel="noreferrer">ToggleButton</a> and <a href="http://google-web-toolkit.googlecode.com/svn/javadoc/1.6/com/google/gwt/user/client/ui/RadioButton.html" rel="noreferrer">RadioButton</a>.
  I want the "mutually-exclusive" part of RadioButton, and the gui look and behavior of ToggleButton(up and down states).
  Does one already exist?</p>