The one-month campaign will see the MiniDisc product promoted on 150 'Viewloo' mini-video screens in 66 washrooms across London, including West End venues Hanover Grand, Alphabet and Propaganda.
The Viewloos will play Sony's 30-second 'Equaliser' TV commercial at broadcast quality.
Located at eye-level above men's urinals and above the automatic hand-dryer units in women's toilets, Viewloos can run up to six minutes of looped ads and content, shown about 10 times an hour.
Although the system currently has pre-loaded ads, the screens will be upgraded and connected to the web over the next few weeks, allowing Captive View to download and customise new ad campaigns from a distance.
Ronnie Rees, managing director of Captive View, said: "Our audience tends to be prolific internet users aged between 21 and 35, which is a very good fit for the Sony product."
The Net MD Walkman allows consumers to download music from PCs to MiniDisc players.
Sony's media agency, OMD UK, worked with Outdoor Connection on the planning of the campaign and Blade on buying.
The original 'Equaliser' TV campaign was devised by ad agency Saatchi & Saatchi.
Brands to have used Viewloos include Bacardi, Microsoft Xbox, Nintendo, Virgin Interactive, Universal Pictures and Siemens.