having renoise as the master would suit me better, but DP5 just wont accept anything i try when its in slave mode.
anyway, using the IAC driver which is built into Macs is the way to do it, set it up in the audio/midi utility (i think bus 1 is automatically set up).
I think midiyoke for PCs is the equivilant.
so you just set renoise up as a slave in renoise to listen to the IAC port 1,
(within the midi preferences) and enable the sync to slave button which is next to the BPM counter on the main renoise page, and it should be fine.
Renoise should now start and stop when you start/stop your other sequencer.
i also am using a program called Jack for OSX which you can use to route audio from one program to another. In this way you can get audio out of Renoise into your other sequencer very easily.
Though obviously you can just render your pattern/track/song and import it.