I’m sure pretty much every WP plugin can be rewritten for MODX, since both use PHP in the end of the day. What MODX version do you use?
I’ve done something similar for Flickr pictures, for Evo. With stuff like that, it basically always boils down to figuring out the 3rd party API, especially authentication, finding out the necessary functions/parameters and how to catch server errors.
Perhaps this can be used as a start:
http://modxcms.com/forums/index.php/topic,32390.0.html