CheckBox

Sample Ribbon XML file:

<customUI xmlns="http://schemas.microsoft.com/office/2006/01/customui">
    <ribbon startFromScratch="false">
        <tabs>
            <tab id="MyTab" label="My Tab">
                <group id="MyGroup" label="My Group">
                    <labelControl id="myLabel1" label="Sample:" />
                    <labelControl id="myLabel2" label="Checkbox" />
                    <checkBox id="MyCheckBox" 
                              label="My CheckBox"
                              onAction="MyCheckBoxCallbackOnAction" />
                 </group>
            </tab>
        </tabs>
    </ribbon>
</customUI>

Attributes: description, enabled, id, idMso, idQ, insertAfterMso, insertAfterQ, 
                 insertBeforeMso, insertBeforeQ, keytip, label, screentip,
                 supertip, tag, visible

Callbacks: getDescription, getEnabled, getKeytip, getLabel,
                  getPressed, getScreentip, getSupertip,  getVisible,
                  onAction

You can find this sample in Sample DB 1