CheckBox "Done" key

I haven't used it myself, but according to the docs, Menu2InputDelegate.onDone() is called.

So I think something like this should work:

class MyCheckboxMenu2InputDelegate extends WatchUi.Menu2InputDelegate {
    function initialize() {
        Menu2InputDelegate.initialize();
    }

    function onSelect(item) {
        //...
    }

    function onDone() {
        // User pressed "Done"
        System.exit();
    }
}

//...

// Create and push your checkbox menu
var menu = new WatchUi.CheckboxMenu({:title=>"Checkbox Menu"});
// add items ...
var delegate = new MyCheckboxMenu2InputDelegate();
WatchUi.pushView(menu, delegate, WatchUi.SLIDE_IMMEDIATE);