The one issue with the ToggleGroup is that it only has one active value at a time - a CheckBox group should really implement HasValue<List<T>>, where T is either CheckBox (or rather HasValue<Boolean>), or is some model object. In the latter case, each checkbox gets a model object mapped to it, probably added when the checkbox is added. Might look something like this:
CheckBoxGroup<Person> group = ...
group.add(new Person("Colin"), colinCheckbox);
group.add(new Person("Darrell"), darrellCheckBox);
Of course, now you need to draw those checkboxes somewhere, and you probably get the model objects from somewhere else too - maybe a ListStore? So maybe this should look more like a ComboBox - give it a ListStore<T> full of T objects, and a LabelProvider<T> so generate box labels for the checkboxes, but then how does it actually draw the checkboxes? All in a vertical stack? In a grid, from left to right, the top to bottom, or top to bottom, then left to right? Scrollbars if it gets too big?
So the short answer is that it is hard to solve this in a definitive, one-size-fits-all manner. My expectation was that lots of people would ask for such a thing, with ideas of what they wanted, and we would flesh it out in a future release, but I think this is the first forum post on the topic. That led me to believe that this isn't a very common problem, or that people build their own solutions readily.