The metaphor was actually pretty apt for the product being demoed: an app for the iPhone, iPod touch and iPad that lets you sign documents or add text or images to your documents and then e-mail those documents back to yourself or a person that you need.
I actually discovered Zosh on my own a few weeks ago while researching business productivity apps, and it's a winner. It really does eliminate the need for a fax machine (or more commonly, the print, sign, scan, e-mail cycle) and is really useful for anyone who is on the go or is just too lazy (like me) to bother with dealing with their printer/scanner combo.
Check out this video:
Once you download the app, you create an account. You can then e-mail any document (PDF, office formats, images) to a special e-mail address that Zosh then imports. Once you get a document, you can choose to add text, a signature or an image (if you have a stored image of your signature or something) and a date.
The cool feature is when you sign the document. Using the iPhone's screen you just sign your name. It works much better than I was anticipating -- it was actually on-par with signatures I create with my Wacom tablet. As you sign your name, the screen moves forward to give you more space. Once you get your signature, you can insert it anywhere in your document, move it around, resize it or rotate it.