FCUUID
iOS UUID / Universally Unique Identifiers library
iOS UUID library as alternative to the old good UDID and identifierForVendor. This library provides the simplest API to obtain universally unique identifiers with different levels of persistence. It's possible to retrieve the UUIDs created for all devices of the same user, in this way with a little bit of server-side help it's possible manage guest accounts across multiple devices easily.