There is a short but useful Google Webmaster Help thread taking place between the BBC UK webmaster and Google's JohnMu. The BBC's webmaster said they are trying to ensure their URLs are the same on the mobile version of their site and desktop version but want to know if that would be considered cloaking.
The simple answer is no, it wouldn't. As long as you serve GoogleBot the desktop version and Google MobileBot the mobile version, and they have the same content, you should be fine.
But often what webmasters forget is that there are two types of mobile sites. One that Googlebot-Mobile should see and one that they should not see. If you have a mobile friendly web site that was specifically designed for the iPhone, Android devices or similar smart phone devices then you do not need to serve that to Googlebot-Mobile, Googlebot will access that fine. But if you have a site that you want to access on those old internet enabled phones, like by Nokia, then you do want to make a special version for Googlebot-Mobile and a special sitemap.
When I asked John from Google about this he said:
Yes, with "mobile" we mean the traditional mobile phone browsers, not smart-phones (which we generally treat the same as desktop browsers given their advanced capabilities). Using special CSS/HTML templates for smart-phones would be fine and would not require submitting them via mobile Sitemap. It keeps things a bit easier if you want to focus on smart-phones, but there are still a gigantic number of more traditional phones with limited internet browsing capabilities out there :-).
Forum discussion at Google Webmaster Help.