Finding entry id in a formatting plugin

Is there any way I can find out the entry id in a custom formatting plugin?

I’m tring to write a plugin that will embed ‘related content’ into the page, but I want the user to decide where this info should appear. My approach is to use a custom formatter that will look for a certain token (ie: {related} ) within the post, and then grab the related item and link it. If I were able to know the entry id from the formatting plugin, I could just query the database and grab all the info I needed and simply replace the token with the link.

I’m not married to this approach and would love to hear alternative methods to gain the same result.