I'm interested in this as well. I've gotten pretty far along with some code. I'm not sure if anyone even looks at threads that are older than a few days, but I'll give this a shot rather than starting another thread.
This code reads the external config file, but I'm getting lost in the looping in a few places:
The querytask seems to be executing only after it's looped through both of the entries in the config.xml
The symbol for the picturemarkersymbol gets used twice.
The field name I'm using for the tooltip isn't getting read properly yet.
It does seem to be loading both layers from the config file though!
You'll need to have a few of your own images, I'm not providing those.
I see that Robert Scheitlin has posted something similar for the search widget, but I didn't see that he'd done one for the live layer. We got caught in that huge storm that hit so many states and it would have been nice to have this functionality separated out of the FlexViewer so I could have easily loaded different data into my own interface simply by updating my config file. I'm in the minority, but I'm not a big fan of the FlexViewer interface.