[RC-Monster Mike]

The slipperential should be available in a couple weeks - waiting for a few parts to get through production at the moment, and tweaking the diff cup. We have been testing a few prototypes with great success, though.
The unit is intended for buggies and truggies, but once I get it off the ground, I will likely make some motor/diff mounts to allow it to be used in other vehicles as well(emaxx, eRevo, etc.).

"alright, because mike's got a patent on the idea, i cant sell them in the US (assuming that mike's patent is a US patent), but because i'm in Australia, his patent can't stop me because there are no 'international' patents.

so i can continue with my idea, just can't sell it in the US (if i even get to thinking about selling it)

so hypothetically , if i were to design a SD, what CD do you guys think i should design it for? (because my design uses a normal CD and attaches a slipper to it.)

remember, this is hypothetical, just forget about any marketing, think as if i were designing it only for myself to use, so no selling or interfering with Mike's buisness."

Correct - while I could patent the idea all across the world, it isn't in the budget right now. International Patents are an option, though and another country will look at US Patents when approving their own, so it is unlikely that someone else could patent it elsewhere.
Of course you can make anything you want for yourself and I wish you good luck on your project. You won't be able to sell them here, though (in US or on these forums). :)