I've never heard of emergency dismounting! I've never been taught that one! What is the purpose of energency dismounts? surely your safer on top of your horse rather than throwing your self off if you get into some trouble? If your horse has bolted for example, jumping off would be dangerous and painful, and unless your horse is ill or extremely naughty, most will stop after they get away from whatever has scared them, and will usually go over or around things to keep themselves free from injury. If you cant stop them, you can usually guide them, so if you are heading for somewhere you dont want to go, you might be able to steer away from it if your still with the horse.
If you think emergency dismounts are essential, be sure to bend your knees when jumping off so you dont jar them, and if you are going to do it quickly then bending your knees should give you more stability. Maybe try jumping off your bed first from a standing position, then try running and jumping on your bed then jumping off and see if you can keep your balance that way. Practise emergency dismounts when the horse is walking, and dont try trot and canter unless your certain you can keep your feet at walk. Try to land and keep moving with the horse, so if hes trotting land and run at the same pace as your horse whilst holding onto the saddle until you get your balance rather than letting go of him straight away.
If your doing this, is the aim to let go of the reins too? the reins may become tangled around his legs and he could run into danger such as onto a main road, although obviously that is better than having you not be able to stop him, hanging onto his reins and being dragged along too.
I think it could be a useful skill to learn, but should only be used in the most serious emergencies and not as a bail out whenever your a bit scared. Good luck with it anyway!