Katie jig NOT new
I would like to point out that the Katie Jig, or the "junior" version of it, is nothing more than a rip-off of the Keller Jig, which has been on the market for many, many years. I've had - and used - one for the past 15 years and am quite happy with it. All that the maker of the "Katie Jig" has done it to PHOTOGRAPH it, and demonstrate it, upside down. This was always possible with the Keller jig - I've done it myself about half the time.
I guess Dave's patent has run out, which accounts for the flood of rip-offs.
Having had a patent ripped off myself, I fully sympathize with Dave Keller, and I wish that people would give him the credit that he's due.
One thing that the Leigh jig and a whole bunch of others CAN'T do is make DT's of UNLIMITED length. Another is make DT's on curved edges. A third is make CANTED DT's: i.e. make a join between two boards at other than 90 degrees, as in a box with slanted sides.
AND it definitely isn't Sommerfeld's.