UVisland Outliner is a Python plugin which does detect the UV island boundaries and turns them into edge selection. The plugin will process all selected polygon objects.
A new option introduced in version 1.1 (available via cog wheel) provides a way to ignore the outer edges of an open-ended mesh.
In general you would want to turn all UV seams into edge selections. In case of open-ended mesh objects, the mesh boundaries would be detected as UV boundaries ... while these aren't actually UV seams. The new option will (by default) allow to ignore these boundaries.
On the other hand you might want to turn all UV island boundaries into edges, no matter if these are UV seams or not. You can do so by unchecking the new option.