Ephedra is related to the active ingredient in many decongestants (pseudoephedrine) and CAN be effective in producing weight loss, both because it raises the metabolic rate a little and because it has some appetite-suppressant properties.
It was recently very fashionable in the US as a commercially available weight-loss adjunct (also known as ma huang). It isn't, as far as I know, being used a great deal in the UK. Yet.
It's also poorly regulated, and in the doses required to produce weight loss (well in excess of what's in most available preparations) it will make you feel unwell, with a fast heart rate, nervousness and agitation. It has been directly linked to several deaths.
If something as cheap as ephedra could be used safely and effectively for weight control, it would be available on NHS prescription. My advice would be to steer clear and if you feel you need something other than diet and exercise to control your weight, go and see your GP and/or join an organised slimming group.