Planerboards aren't exactly slip bobbers, but has anyone actually tried using them for catfish? That idea has been rattling around in the back of my head for a couple of years now (lots of room there). I've never even had one in my hands, but from what I've read, and what I've seen on TV, it seems to me that they might prove very useful for catfishing. Of course, either the planerboard or the water has to be moving, so they couldn't be used in every situation, but lots of fishing situations fit the requirements.
1. Anchored boat or boat drifting down the current using a drag or trolling motor to drift slower than the current. A planerboard on each side of the boat would give a much wider spread to your hooks, keeping them from all swinging down directly behind the boat where they cover less ground and are likely to tangle. Also, your terminal rigs are generally kept off the bottom, so that you wouldn't hang up as much. Seems like it should be the same as floating hooks below a bobber or jugs; you're just getting a better spread.
2. Bankfishing. When you're bankfishing where there's a strong current, you either have to deal with your sinker/bait drifting downstream, and keep recasting, or you have to get your sinker to hang up, which generally means that you lose your sinker. A planerboard should take your rig out at a pretty sharp angle, and keep it from washing in to the bank. Furthermore, the planerboard does do duty as a bobber, keeping your rig off the bottom. Now, I can see a problem of how to keep the sinker/bait from hanging on the bottom when you're putting out your rig from the shoreline, but that simply requires something that will dissolve, come apart, or weaken after being in the water for a few minutes, so that you can get the planerboard out, wait for the gizmo to come loose, and have your line drop down in the water to whatever depth you have set.
3. Drifting across a lake, either pushed by the wind, or by a trolling motor set on low speed. The advantages are the same as for #1. Seems like the slower you drift, the larger the keel you'll need on your planerboard, but that's just a small technical problem.