Is it possible to use SinOsc.ar(200).that(....) on any Ugen within a SynthDef? I really enjoy using LFO values in visualisations etc. via That.identity but having this directly available would be great as in such a case I would not have to create multiple sub-busses/Ndefs.

Could this be implemented by wrapping the Ugen with a SendReply which is setup according to the That specification?
A first sketch could look like SinOsc.ar.that(callback: {|r| myVisualOSC.sendMsg("/foo", r)}, trigger: {|in| in>0.5}).