Yay, BopIt -- helps with impulse control as well as sensory seeking needs.
We have an oval trampoline from SpringFree, which is tucked in a corner of our typical small suburban garden . The oval shape limits the number of kids doing tricks on it, because you can only go in one direction and it makes for a smaller footprint. Ours is 8x12 -- I would never dream of a 12' plus edges in our backyard. SpringFree trampolines are expensive, and hard to find second-hand. But they are safer, since there is no spring frame around, and the side walls are sturdy and bouncy. I don't feel like I have to hover over my 5 and 8 year olds, but I will supervise when the neighborhood kids join in.
Other outdoor goodies: a zipline and monkey bars; Tall swing off a tree branch (the playset ones are way too short); Scooters and bikes if they don't have one; stilts.
Big huge bucket of chalk, empty driveway and friends to paint with.
Indoor: pottery wheel and clay (get the sturdiest one you can afford. Better to have a mechanical one, used, off Craigslist than one of the kid toy ones, if you can afford it. It may well become a grown-up hobby as well. But the kid one was still a huge success in our house. )
Playdough and paint are still a big hit in our home. For a girl (although my boy also loves it) the Rainbow Loom (Michael's sells it) allows them to make bracelets out of rubber bands -- much better for sensory kids than doing the old-fashioned way, with thread strands.
A portable CD player with CDs -- I know, all your music is on your iphone / computer, but kids still like to handle their music and look at the pretty jackets!
Yay to beanbags, but don;t get the styrofoam ones, they get squished down in a few months. Especially with a sensory seeking child who will soon discover they can squish the pellets bubble-wrap style. See if you can find something filled with non compressing pellets. Maybe even actual beans! Also, a fuzzy moonchair/sauccer chair for reading can be a big hit for a 2nd-4th grader.
etc...