Garrett St. John wrote a clear example on how to use UUIDs in Eloquent models. This kind of logic could go in a trait so it can be reused across multiple models.

By default, Eloquent uses an auto-incrementing integer as the primary key for its tables. While most of the time this is totally acceptable, sometimes there is a need for primary keys to be less predictable.

http://garrettstjohn.com/entry/using-uuids-laravel-eloquent-orm/

EDIT: Kirk Bushell has made a trait for this functionality. Take a look at his Eloquence package on GitHub.