I haven't seen the ones that jig the whole rod... but have seen the ones that clip the main line and jig that. I can definitely say they work. Saw it with my own eyes... about 75% of the fish caught when we used one, came from it. (Even though that one line was up against three others... 2 leadcore and one downrigger)
I have one I installed a few years back. I picked it up a paugus bay before Jason parent bought the store. He has his own type of jigging machine at his store if you want to see it in person. The one Ihave is a different type. I run my fly rod in it early season and it works great!!! In the later part of the season I will run the lead core every once and a while and trust me it does work. The motor that jigs is a windshild wiper motor geared down from what I have been told.