drawflex

Hello people, lil bit of guidance required please.... I'm in the process of designing a pretty simple usb midi controll surface built around a core32 module to use with ableton live 8, and there's one thing i cant get my head around yet... i understand about mapping inputs eg.. faders/sliders/knobs and what-not but am unsure of were i get my output data to drive the various indicator LEDs that i see everyone using ??? eg beat indicator / incicators for which scene/track is playing / data to drive a tripple 7 segment led for bpm / level data for a VU.....can it be done from inside ableton or does it get a bit heavier than that ?