As per groups post https://groups.google.com/forum/#!topic/zotonic-users/Ky0WKIevHtU
When viewing the site from an iPhone, Zotonic should automatically select the best classification (being phone). However, 'desktop' is always selected.
The cache on the phone has been cleared and the user-agent confirmed as "Mozilla/5.0 (iPhone; CPU iPhone OS 6_0_1 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A523 Safari/8536.25"
Was a problem with building the ua_classifier nif.
This has been resolved with better error messages.