I modified the Google Maps Extension to read KML files, using as reference the link below:
I now have a parameter where I can reference a KML file.
Please let me know if you want some help.
You can get if from here: https://dl.dropboxusercontent.com/u/56013581/GoogleWidgets_ExtensionPackage_KML.zip
Using it is very straight forward: just add an URL for the KML file in the Widget property and it should show the layer with the routs or markups.
Unfortunately I am not generating a KML file yet but you can find many tools online that do that.