The Portable Video Player like device has a 3.5" Screen and uses iVDR mini (iVDR stands for information Versatile Disk for Removable usage) drives as storage. Exhibit attendees can carry the device around and view additional information to the exhibit. Hitachi obviously wants to show-case that their fuel-cells really work. 

What is iVDR: 
"iVDR" stands for Information Versatile Disk for Removable usage. 
a lightweight, compact, removable hard disk drive. 
a removable medium having the large capacity and fast random access. 
a medium which has interface (signal unit) conforming to Serial ATA, for as high data transfer as 1.5Gbps. 
a medium which enables users to construct servers with TB (Tera Bytes) capacity easily using multiple ones. 
secure standards based on PKI (public key infrastructure) prepared for realizing record data information protection and copyrighted digital content protection. 
The iVDR is a new medium that provides shared data over a broad range of markets such as home servers, video recorders, automobile AV devices and computers.