Someone, in "Welcome To Macintosh," said that Apple spends a lot of time and money designing their products, like MacBook (Airs, Pros, etc) to just work mechanically with little effort. And that aspects like hinges, handles, and levers are designed to work very simply, while being very complex, although the average individual would never realize it.
But it's only compatible with iPhones, for now.
But it does make sense to be able to use Google Voice on an iPod touch/iPad because some people use Skype and/or Gizmo5 which, when used with an iPod touch/iPad, would allow calls to be made very inexpensively or for free.
Skype calls on an iPod touch/iPad with Google Voice would be great. Gizmo5 calls on an iPod touch/iPad need the Google Voice app to work on them.