CamRanger, mentioned above, will essentially turn your iPad into a large remote rear panel. If you just need an intervalometer, Trigger Trap has all kinds of timing controls (time lapse, distance lapse, star trails, precise bulb timing,...) and runs ...
I had the same problem and went with the S110. My regular camera is a 5D MKII, very nice, but too much to carry around all the time. The deciding factors for the S110 were the price (it's a 2nd camera, not my one and only) and the WiFi. I got it more...
