We have built a tool, based on a Wordpress plugin, for users to sign up to be a part of a database for a film/TV casting company that routinely searches through its database of paid users for individuals who meet a certain criteria, and then sends them an invite to participate in a shoot or audition for a role. The major strokes are already in place, however there are a few features that need to be integrated still.
Users register on the site, then subscribe annually based on a PayPal recurring payment. They enter information about themselves pertinent to the casting agency (height/hair colour/resume/etc) and are added to a database. This database is searchable via the app, and when appropriate candidates are selected, they're sent an email inviting them to participate in an audition or shoot, which they confirm on their end.
That's it - the broad strokes are already in place, however the email invite/sendout needs to be integrated (ability to search and then invite a number of users at a time), as well as a calendar function for the client to be able to schedule casting calls.