Point locations in the new Flex API for AGS are rendered using a Symbol subclass. One of these classes is the InfoSymbol, where an info window (callout) will be displayed anchored at the point location. Developers can specify the content of the symbol as a DisplayObject sublcass. The InfoSymbol was inspired from the FIG: Callout Component.
Below is a sample. Click on it to see it in action, and you can download the source code from here.