All this stuff goes on at the model level right?

application_helper may not be the best place for these. This was kind of an unfortunate choice of name by Rails, but /helpers/ are supposed to be for view helpers.

You get some unintended things happening such as having these methods exposed as controller actions because they are included in controllers (?!) (don't worry, if we don't have any routes to these nobody should be able to get to them...). 

I might prefer to implement this as a concern (a what? more brilliant rails naming choices...)
http://richonrails.com/articles/rails-4-code-concerns-in-active-record-models