While Canon products at times have a price markup for items that bare the label (like Harley Davidson products) there are a few gems that are good deals at the price point. The Canon backpack and the 50mm 1.8 lens are examples of good deals. This switch also belongs in the 'worth the price' category.
The switch connects into the side of the Rebel XT. The female receptor on the camera is underneath a rubber cover. The cover folds back awkwardly/protrudes when the switch is connected. This is mildly annoying, but not a big deal.
The switch is simple yet effective: half push for focus, full push to take the picture, or push the switch forward to lock the shutter open (for night shots, lightning, etc.). When pressed forward, the shutter remains open until you pull the switch back into place. You don't have to hold the switch open as it locks once it is slid forward.
The switch can activate the shutter either in the single shot mode or the time delay mode. Single shot or time delay are set on the camera, not on the switch.
In single shot the shutter is activated as soon as the button is fully pressed. In time delay, fully pressing the button starts the 10-second countdown prior to the picture being snapped (time to run in front of the camera for family or self-portraits).
For macro shots, night shots, or shots in which minimal or no camera shake is permissible this inexpensive device is quite useful.
Finally, it has little notches built in to the side of its body to help hold the cable securely against the body when the cable is wrapped up for storage. It also has a slot to plug in the male attachment (the part that plugs into the camera) built into the body for convenience in storage and to protect the connector when not in use.