Hello Michael,
There are several different ways you could accomplish this. You could do so via the built-in callout's customView (which is essentially just a UIView), or just roll your own view (and optionally view controller). For example, we use a "bottom sheet" UIView which we animate on, up, and down the screen, while dynamically updating data as it changes via notification handler methods in the map view controller (though, we could just as easily have embedded another view controller in a container view, or presented another view controller over the map view controller context).
It is my experience that customers typically end up wanting more and more functionality that tends to push the bounds of basic classes like the AGSCallout. I recommend taking the only slightly greater effort (in the short-run) to create a custom view that gives you exactly what you need.
If you're interested, I'm happy to show you some sample code.
Cheers,
Jake
