Sharp just came out with the craziest overblown electric dictionary. The Sharp PW-C5000.
I don't know how it rates as far as usability for studying Japanese but it's not only got a Japanese dictionary, an Japanese to English Dictionary, an English to Japanese dictionary like all the others, it's also got a health and medical info book, 2 recipe books with pictures and a Visual Encyclopedia. 17 books in all. Check to some screenshots