I bought the EZA-C3 for my Canon EOS 7D because I wanted to use a cable release with mirror lock-up, as well has having the option for timed shutter releases (both countdown and time-lapse). This unit provides all of those functions in a cheap, convenient package. In your camera's normal one-shot mode the shutter button on the remote works just like the camera shutter button: half way to expose, all the way to shoot. It can be locked down for bulb exposures. There's also a timed mode which lets you set an interval between shots as well as shot duration and number of shots, so you can leave the camera to its own devices shooting time lapse sequences.
Construction is incredibly cheap and tacky. There is no way to turn off the power, so you may wish to remove at least one of the two AAA batteries when not in use. The cable interface is N3-type.
Build quality and the missing power switch lose a star for this unit, but it deserves the remaining four purely on the basis of the possibilities it adds to your repertoire.