You need a Roku device with the MOG channel installed (and a MOG.com subscription, obviously), and Google Chrome.
Latest version (Morgku 0.0.3) - Install (source code)
After installing, you need to configure Morgku by going to Tools->Extensions and then options.
The extension adds "Roku" links to songs, albums and playlists wherever it can find them. You have to browse to an album or playlist's main page for it to work, for example here.
Morgku was written by Oliver Smith.