I just saw a thing on TV..they now have a collar that has a cell phone built in with GPS capabilities. On your phone you can get co-ordinates on your dogs location and you can listen to him bark. This is mainly for bear & **** hounds of course.
I agree with bloodtrails. The most important thing is to teach the command first and only use the ecollar to enforce a command the dog clearly understands. Perfection Kennels has two great videos called The Perfect Start and The Perfect Finish. It's a simple method that works really well. The link is http://www.perfectionkennels.com/. I use a collar from DT Systems and it seems most of the Pros like Dogtra Collars. Before I used the collar I was worried I would be hurting the dog but I have found the ecollar is really harmless. My pointer goes nuts when I take the collar out of the box because he knows were going hunting. A good web site to buy one is http://www.gundogsupply.com/dogtrainsupe.html . Good Luck.