Scooped! Kite "line climber" already patented. In 1893.

Gosh darn, but do I love the internet.

Adi Shavit just pointed out in a comment to my Kite-Launched Skydiver Challenge that similar devices for running objects up kite lines have been around -- and patented -- for years. In fact, he has posted a 1903 patent and a 1893 patent for just such devices on his Kite Patents blog.

Although the British one uses 2 paper clips, it is essentially identical to your version. By making a small groove in the straw bottom, you can get a similar effect without the hook coming completely out of the straw.

There are many other similar designs, and especially ones with collapsible wings which pull the kite up until the apparatus hits the stopper. The wings then collapse, the payload is released, and the whole shuttle comes sliding back down. It's been a while since I built one of those, but they do work.

Some other cool kite patents from his site:

• Captive helicopter kite (1947 -- apparently patented by the inventor of the Bell helicopter)
• the First Kite Surfing Patent (1977)
• and the wonderfully Rube Goldberg Waldman's Fishing Kite (1967)

Thanks, Adi!

And as for my own design...I'm still awaiting a good windy weekend day to try it out.