space.listeners.add(new BodyListener(CbEvent.WAKE, CbType.DEFAULT, function (b:Body) {...});
space.listeners.add(new BodyListener(CbEvent.SLEEP, CbType.DEFAULT, function (b:Body) {...});

or if you only want to handle when a certain 'type' of body wakes/sleeps.
var type = new CbType();

then assign that type to the bodies; and then:

space.listeners.add(new BodyListener(CbEvent.WAKE, type, function (b:Body) {...});
space.listeners.add(new BodyListener(CbEvent.SLEEP, type, function (b:Body) {...});

so you only get an event when 'those' specific bodies are woken/sweffed