ISO developer (paid) for custom app/plugin

Hi!

I need an app/plugin option that will automatically send a notification or direct message to a user when they tag another (specific) user. 

This is how I would like it to work.

1. Lucy is writing a post and tags "@John".
2. Lucy automatically gets a direct message or notification alert with a message.
   1. Message/notification would either
      1. Contain a video & text embedded within OR
      2. Contain text + a hyperlink to a specific page (where we can embed a video).

Please let me know if this is something you can help develop.

Thanks!