I remember that chirping ball thingy. Never bought it or heard of anyone trying it. I think it would be good for Bobcats.
I think blind sets would work with chirping ball.
But a well constructed dirt hole on good location is hard to beat.
Years back, the ole timers told storys of burying a pocket watch under a blended trap. Fox would be caught by both front feet.
I never tried this method either.
When I was young, I had one pocket watch and wasn't about to use it to catch Fox. Dad would tan my hide if I messed up my watch. Mom tied a brown shoe string on it so I wouldn't lose it...LOL.