Hey Rob,
I haven't done much BJJ, but have trained in Aikido, TKD, and Krav Maga. On top of that, did some VERY informal Muay Thai, Boxing, and stick fighting.
So far, the most PHYSICAL (though not NECCESARILY practical, though not necessarliy NOT practical, either...that's just a different discussion) changes and best bet for gettig into better shape, has been Krav Maga. We start each class with a great half hour "warm up" which often involves cardio, sprints, drills, jumps, push-ups (100 in 4 minutes max) crunches, defenses (also knwon as air-raids), jumping jacks, etc. The end of the warm-up usually sees me stretching out and changing my first shirt. The remainder of the workout is more drills and skills, and might work one or two main muscle groups very well, depending on what you are working. Feel free to PM me, as I love to chat about this stuff.
BJJ required one to already be in decent shape, flexible, etc where I took it. It would, depending on the school and the types of classes they run, very possiblly be just as effective as the KM school I am in now.