Create phone/tablet apps, or make it easier for third party developers to allow users to view custom user lists. At the moment I can't find too many apps that let me view my custom lists. I can't find any on Android, although Windows 8 has Watchlist which is a great trakt.tv app.
We offer the APIs for custom lists, so its up to the individual apps to implement those features. I would recommend reaching out to the apps directly and suggesting support.