Add activity history to calendar pop up

How would you approach this request?

Our inside team sets follow up tasks when they can’t reach someone or when they speak to a prospect and the person asks to follow up later.  We’ve given the inside team a Calendar component to see all of the follow up items for that day and they’d like to be able to see recent activity with that lead/contact in the Calendar pop-up.

How would you approach presenting that information?

It’s similar to this concept but on the Calendar pop up window:

The calendar component can take multiple models as event sources.  One source could be “My calendar entries”  and the second source could be “Entries with this Who_Id”   You can use different background colors for each one to help your team differentiate. 

I have 2 calendar sources now - tasks and events (both filtered by they ones they are responsible for).  The events/tasks are across multiple leads/contacts so they wanted to be able to click into the task, see the notes and look at their recent activity with that specific lead/contact.  Does that explain a little more clearly?

I have 10 tasks due today with 10 different people - when I click into my notes about that task, I want to see what my recent activity with that person is.