Writing a plugin that notify my friends of new post that mentions(@) them

For example, I write a new post with content “Today I’m happy, because I finally met the girl that @David told me about bla blah…” Once the post is published, there should be an email notification sent to David about this post that mentions him. Is there already such plugin? If not please help me with my implementation. Thanks a million time! 🙂

How to Use Checkbox in Custom Option Page Using The Setting API

Can you please let me know how I can add a checkbox to Setting API in creating Custom Options Page? I am using the following code to add a txt box which is working perfectly but I am totally confused how to add chechbox to the setting API and options. I just tried ti update the input type to checkbox but I am not sure what to put in Value besides when I save the form the check box still appears unchecked!