Looking for "Buyback" Plugin (something like uSell.com, Gazelle.com, Glyde.com)

Looking to offer "buy-back" options to my customers - perhaps with cell phones.

Trying to find a way to do this easily. Similar sites are glyde.com, uSell.com, Gazelle.com

Does anyone know of a plugin that would help me set this up? Or a theme integration with this?

Thanks!!