I just bought a wireless remote from Ebay for about $25. There are several "brands". Most are made in China and sold from Hong Kong. The one I got was branded "Aputure". You'll see lots of mention on POTN about Phottix. My guess is that they are all quite similar.
Mine works like a charm. It says it will work from up to 30 meters, but I've only tried it from about 30 ft. so far. I'm looking forward to trying this out with our bird feeder soon: sit inside with camera on tripod near the feeder and snap when birds are there.
That is one of the main reasons I would like a wireless remote. Would like to set up the camera outside and focused on the feeder then be inside clicking away. I have (and use a lot) the Canon wired remote and like it very much.



