DSLR Controller was the first and is still the best app to fully control your Canon EOS DSLR from your Android device, with nothing more than a USB cable. No computer or laptop required, no root required. All you need is a compatible mobile device, a compatible camera, and the right USB cable. If you have Wi-Fi-capable EOS model or a WFT box, it also possible to connect via Wi-Fi.
ALTERNATIVELY: Do the same thing with the even cheaper Nexx WT3020!
DSLR Controller is the oldest and most complete app to remote control a Canon EOS DSLR from a smartphone or tablet. It offers you remote liveview, control of most common settings, capture, focus and zoom control, image and video review, timelapse, HDR/AEB, focus bracketing - and much more! See the about page for a full list of features, system requirements and screenshots.
DSLR Controller has been covered by several large news outlets, as well as a number of magazines. A prominent core developer of Android itself even called it his app of the year.