The ability to trigger a notification to a specific once a customer has completed a stage in journey

Description 

Custom Action in a Journey that triggers a notification event   

Why is this feature important to you 

When an email is sent to a specific audience group, I want to send a notification to the Sales rep (On customer profile0 immediately to set up a call or follow up action. 

The ability to create a custom action would be great.   

How would you like the feature to work -

I want to be able to build this custom action in AJO by our admin team so that users can drag this into a journey.  When a customer profile moves through the stages in the journey it will pass through this action, which will trigger a notification to a preset email.   Ideally when building the custom action, I would be able to set up the conditions that if Rep ID = X then sent corresponding Rep email address.  The notification could be a basic  email that lets rep know that customer with Customer ID has reached a specific stage  

Current Behaviour -

Cannot find a solution for this in AJO, though all the capabilities described should be feasible within what the platform is capable of today.