Aputure Gigtube Viewfinder for Canon 550D
Just ordered the Gigtube and a 50d. I got the last Gigtube Adorama had in stock. Should arrive on Wednesday.
I'm anxious to try this out. I see it as more than just a flexible viewer that you often see on the compacts. With this you got the shutter release built in and a 6 foot extension. This should enable lots of new creative options.
The first use I can think of is with a giant (20ft) monopod with an addition of a longer cable extension.
Another use could be mounting the camera setup on Bogen Magic Arm with Superclamp attached to a low vantage point on a bike. This is just one example of dramatic motion shots that could be made more practical with a setup like this.
Of course, there's the camera / bait trap for wildlife photography. This device gets you away from the camera so the wildlife will come near AND lets you see what you shoot for the best timing.
The Lilliput 7" HDMI option mentioned earlier is much less compact and does not have an internal battery power option. If you look on ebay, you'll see these things mounted on camera hot shoe and it's bigger than the camera! Sure for some off camera applications, it would be nice. For the majority of situations, the Gigtube fills the niche much better. A little pricey yes, but there isn't much to compete with it at this point.
If you want something less expensive; go to ebay and look for "Wired Live View Remote". Here you will see a model created by the company Yongnuo. This model is priced at $100, but is only a remote shutter release and viewer; no hot shoe mounting and it looks cheaper than the Gigtube. Also, I am trusting Adorama's choice to carry the Gigtube and no others.