if i got the platforms how hard would it be to connect it to a wheel and would it take a special wheel?
Mark 
it would take a wrench and about 5 min.
depending on the axel diamiter, you my need to get a wheel with the corect axel size.
E.
it would fit on a bike wheel right?
A ordinary bike wheel is to prefere, since the axle goes trough the hub, so your platforms are connected to each other.
If you use a wheel with a unicycle hub, the platformst won’t be in contact, and they may spin with the wheel since there is only half the weight on the bearing…
Use a regular bike wheel, preferibly with from a BMX, with longer a longer and stronger axle.
But any bikewheel would probably work out fine, for awhile at least.
We did the same thing, bent (with heat) some flat stock steel and drilled for the axle bolts. put it on a bmx wheel. The idea works simply and easily as long as the axle is strong enough. In the case of our little fabrication project, the axle simply bent down with the force of the platforms when you stood on it. We didn’t even try jumping starts because the axle was bending simply from gently standing on it. We would get a few good rides out of it before having to tweak it back into place.
Hope your’s works better, or maybe we just had a cheap bmx hub and weak axle. If anyone has any suggestions, I’ve love to hear them. Riding the wheel was insanely hard and scary, but really fun.
-Jeremy
Use a BMX hub with a 14mm axle rather than the weaker 3/8" axle. The 14mm axles are larger in diameter and stronger and shouldn’t bend like the 3/8" axles will.