This App for the Iphone or the Ipod touch is a great and has functionality too.  Let me put you through the steps.

You go to Itunes and do a search for DSLR app.  Pay for professional DSLR and download app and wait or it to install. Next you go to www.ononesoftware.com and go to DSLR and download server.  Then install this on your computer. 

To make this work you must make an ad-hoc network on your computer.  Ononesoftware has some great examples of how to do that.  Once that is done turn on and connect your Canon DSLR camera to your computer via USB2 cable. Then launch server software and now start the program on your IPOD touch or IPHONE.  It will find the ad-hoc network then your ready to go.  It seems that you have to set the mode on the camera to ie: manual, program, etc.  Then the magic starts you get this great interface which allows you to change your camera settings, ISO,  then your ready to fire your camera.  The image shows up on the screen quite quickly and is very color correct.  I was impressed with this feature.  If you double click on the place you would like enlarged you just double click and it will zoom to 100% then double click and it goes back to normal.

If you have a Canon camera that has liveview and is recognized by the program (ononesoftware has a list )  To do this you must press and hold fire button down until you get the menu with liveview.  Then just click liveview and vola it show up on the IPOD touch or IPHONE.

In my opinion this is quite useful for self portraits or commercial portraits where you need to see the changes in lighting and you are by yourself.