The National Library of Medicine has newly redesigned these sites. They are optimized for mobile phones and tablets. Unlike the original mobile sites which only contained a subset of MedlinePlus, the new sites have all the same content that you find online.
The newly redesigned sites also now offer improved navigation using menus, enhanced page navigation with the ability to open and close sections within pages, and an updated look and feel.
In the next phase, the MedlinePlus team will launch a fully responsive design that will allow for a consistent user experience from any point of access, whether desktop, tablet, or phone. NLM anticipates a release in Spring 2015 of its fully responsive versions of MedlinePlus and MedlinePlus en español.
More details are available from NLM.