This is probably known by most of you out there but just in case, smartphone URLs will not show up as mobile URLs in a mobile Sitemap.
A Google Webmaster Help thread has one webmaster asking why his mobile sitemap is not being indexed. As you can see from the graph above, the web sitemap is being indexed (blue is submitted URLs, red is indexed URLs). The mobile sitemap is just submitted but not indexed.
John Mueller of Google said they treat smartphone URLs the same as desktop URLs. He wrote:
Is it possible that the URLs in there are not traditional mobile URLs, but rather smartphone URLs? Given that we treat smartphone URLs as being equivalent to "normal" web-URLs, they wouldn't be counted separately as mobile ones (where we'd only include those specifically for traditional mobile devices using WAP/WML,etc). If these are smartphone URLs, I'd just include them in a normal Sitemap file and submit them like that.
Again, this is something that is likely known by most SEO experts but just in case.
Forum discussion at Google Webmaster Help.