I checked this product out at PMA and it looks super. I even had them inspect my 5D and they saw two tiny dust spots which were too small to mess with (it was cleaned recently with the Arctic Butterfly). Since the two tiny spots were so small, I was told it wasn't necessary to clean the sensor. So having the ability to see the condition rather than arbitrarily cleaning the unit made a lot of sense to me.
This makes no sense to me and it sounds like the marketing guys got to you. Just focus on infinity, mount a flash, set to f/14+ and your sync speed, focus on inifinity, and then take a photo of a white wall from a 10 cm away. Then look at your shot and see if there is any obvious dust.
I say this makes no sense as one can do the same this exact same test (looking for dust) with the mirror up, shutter open, no lens to protect the sensor, and even more dust, dead skin, pollen, and sneezes getting on your sensor using the new tool or less exposure using the old tool (your camera).
It does look like a cool tool for finding what dust to clean after the camera is opened, but it is a very poor choice of dust detection tool for deciding when to clean as it fails to account for both the optics and apertures you use and opens one up to sneezes (the guy 3 m behind you can hit your sensor with a sneeze) and other bodily functions (coughs, breathing, talking, ...) that emit particulate matter.
some thoughts,
Sean (who has cloned/healed way too many dust spots in boke* and a rare few in details)
* Dust spots are statistically unlikely to be a major issue in in focus areas where the relative collimation of light rays is high creating tiny shadows on the sensor unlike the huge shadows OoF light creates from tiny dust spots.