both good guesses. Obviously not the second one ^_^
The first one's a great idea for a product ~ does that exist? That's much more of a logical answer than what the product actually is. It's pretty tricky,

Okay, here's a clue: the name isn't one you'd be likely to come up with for this product, the words more or less make sense for it, but it sounds like a name that was come up with by a non-native english speaker.

While you ponder ideas of what it might be, let's see how many different definitions of a ghost duster we can come up with. Here's a few:

A coat worn by a ghost, or a coat that has returned from the grave.
An temp on the police force who checks for fingerprints under the name of a higher-up detective (similar to a ghost writer)
A dust storm that blows right through a midwestern town without any damage.
The jacket of a book of scary stories.

(Note: none of these are what the actual product is, obviously... but how many more can people think of?)