As for alternate forms of cardio, a Concept II rower is the only "cardio" machine worth owning, IMO. Good vids on its use at the Crossfit site. Next I'd reccomend a Stairmaster PT7000 Stepmill one or two days each week if you can find one. This is essentially walking up a down escalator. This can induce patellar tendonitis if you over do it, moreso the shorter your legs are, as short people have to flex the knee farther to reach the step height. Pushing or dragging a loaded sled or flipping a 3-400# tire will definetely get your heart pumping.
If you get bored with your Concept II here's one to spend some time with:
