Thought you were just looking for something to play SMF's with markers. You haven't got anything to play them INTO?

Just a thought, but doesn't the MotifXS have a Marker function for its' sequencer? Maybe a rack version of that would do the job?

If you simply want to play MIDI into gear you already have, a large variety of sequencers (and Ableton Live) can do Markers, and as long as you aren't trying to get the laptop to be the sound source as well as the player, it shouldn't be THAT difficult... probably no harder than grokking a decent arranger or WS, anyway. Nothing is THAT easy, these days!