This may not be considered a "cheap kadee uncoupler" but it's an excellent replacement for Kadee uncoupler ramps. It can be located anywhere in the track system. This system is discreet, strong and reliable. I've successfully used this system to remotely uncouple cars for years.
The heart of this uncoupling system is "Magcraft (rare earth) Magnets. I use the .125 diameter x .250 long (pt # NSNO576/N40). 50 rod magnets.
I prefer using a 6" long 1/8 drill bit. Drill 3 holes ON EACH SIDE in the spaces between the ties - anywhere from 30 to 45 degrees against and under the rail. The intent is to drill a hole deep enough so the top of the earth magnet is at the same height as the tie. The magnetic rod is + on one end and - on the opposite end. Insert (3) + side up rods on one side of the track and 3 rods - side up on the opposing track side. Secure with silicone or CA. Generally 3 rods (each side of track) are sufficient. Occasionally Murphy requires 4 magnets each side ? I've successfully planted magnets in a wood planked boat deck and covered with wood putty - works well and is invisible.
The uncoupling process is to slowly power into,, over the earth magnets.
You'll see the Kadee couplers snap apart. Reverse direction, power back in to the open coupler and you can push (spot) your uncoupled car. Normal driving over the magnets don't uncouple the couplers. Of course coupler height and adjustments are critical.
I also have bamboo kebab skewers scattered around the layout.
What I enjoy about this system is that after extensive operation I can determine a necessary location to place this remote uncoupling system. 6 holes later and I've made a new uncoupler site.