For hardcopy, I’ve been relying on Nintendo’s helpful dictionary for the DS; though it’s Japanese-Japanese (and English-Japanese), and the interface is Japanese, so a certain amount of understanding is required. Even if you can’t read the definitions, though, you’ll at least get the kana (syllabic pronunciation) corresponding to kanji words, so you can then look it up much more quickly in your Japanese-English dictionary. The Japanese definitions leave something to be desired, anyway; they tend to be quite terse, and not always entirely accurate. The handwriting recognition, however, is quite excellent.