Looks great! I think this would be great for anyone looking through online classifieds, so that posters could include a mobile friendly media (placeunit) link. Is that your main target?

Do you have any plans to charge for this service?

There are many "angles" for utilization. Mobile friendly linking is a great idea. There is an auto implementation for Twitter cards in the Units BTW.

As for charging, it is a little premature, but if you want to attach a domain this will be a paid service.