I've used one of these cheapo's off ebay on my 400D for about three years.
HERE
I've never had a failure and the batteries still don't need replacing. The specs say its working range is 10-15 metres but I've used it at 25 metres with no problems so It's great for wildlife shots from a distance.
If you do decide on one of these, remember to peel the almost invisible plastic seal off the CR2 battery in the receiver.
I thought mine was knackered untill I worked this out
