There is no automatic way to generate a route at the moment, but James seems to be really interested by the algorithm.
But it is possible to build a route following all the connected streets of an area.
To generate a gpx file, you have to download your city streets in an GIS editor, opensource QGIS submitting an OSM query like citystrides do.
After that, you select the area you want to run and call a plugin called CPP solver that solves the route optimization problem.
Then upload the gpx route to your watch app like I do
(see also Chinese Postman Solver discussion)