Seeing your device made me wonder what other ideas are out there. Here’s something I stumbled across that I will probably try out. It's cheap and got pretty good feedback at Amazon, including the comment below. I suspect it might take a little more finesse than yours, as it only provides a loop as opposed to a big square like yours does:

http://cruisingsolutions.com/product/docking-stick/

"For years I jumped off our forty-two foot sailboat to help my husband dock it. Last year my knee gave out. I've been searching for something I could use from the boat to help tie us to the docks. The Docking Stick worked perfectly. I can stay on the boat, hook the dock cleats, and secure the boat without getting off. My husband and I are thrilled."(nl)

edit: it gets favorable comments from a couple sailors here as well:
http://forums.sailboatowners.com/index.php?threads/docking-stick.161948/&highlight=Docking%20stick