My ds uses fiddle toys during assemblies, as he really struggles to sit still and not talk to the children around him. His inclusion teacher tried a piece of silky string and blu tack with him first and they do help sometimes, but not enough for assembly, so he actually has a tangle toy for that now. He still uses blu tack in class while his teacher is talking though and it does seem to reduce fidgetting slightly.
In his case, he needs to be fiddling in order to take in what the teacher is saying, rather than the fiddle objects being used as a distraction. It's almost guaranteed that if he' sitting quietly and looks like he's listening, he hasn't taken in a word. If however, he is looking everywhere but at the teacher, wriggling and fidgetting etc, you can ask him anything about what the teacher's said and he can answer you in a heartbeat.
He also has a wobble cushion that looks extremely similar to the one you linked to. Reports from various teachers seem to suggest that his bottom isn't actually on it long enough for it to help all that much! 
He didn't get on with a move'n'sit wedge. His teacher felt he was more using it as a slide than actually sitting on it! I do know of two other children that have them though and they've found them very good for helping with good posture and writing position.
Ds also loves his Jacobs Ladder, but I wouldn't recommend it for school because it clatters as it falls. He has a wooden one that my Mum bought from a National Trust gift shop when he was two and he's always been fascinated by it, although he sussed out how it worked within half an hour of being given it!