[colechristensen]

Didn't Apple buy up a bunch of companies and patents that enabled their various touch control devices?

Here's one https://en.wikipedia.org/wiki/FingerWorks

I remember another one for the iPod interface but don't want to put that much research into it.

I think it comes down to patents and getting a bunch of small things just right... which you can do if you're Apple and you own the full stack, but is much more difficult supporting all the rest of random hardware.