Either stopshot with highspeed shutter and crossbeam lasers (ie bugs in-flight kit which I can expand on with IR sensors later for general motion stopping outside of larger subjects)
It's almost 2 halves of the same setup since if I get the latter I'll have all the lighting I'll likely need for a very long while and mobile whilst the former gives me the trigger setup that I can use (with lighting) for highspeed photography (my biggest limit with that is that I've at present only the macro flash units and a single 580EX2 - which puts out good light but is rather one directional being just a single flash).