Ok, not really a favorite tool yet, but it’s just arrived and I plan to put it to use this year as I start work on some windsor chairs. Peter Galbert has this available via Benchcrafted now, so you can order yours if you find that you want a jig to help sharpen your draw knives.
I saw this jig at WIA a couple of years ago. Does the job quite well.
It looked like it was set to do a good job for long blades. I just saw Chris Schwarz’s blog post on the same thing!