I'm not sure if it's my new Keitai's browser, or if the keitai pages have been tweaked, but Jim Breen's WWWJDIC now works on my Vodafone. The WWWJDIC site says it works on DoCoMo, Vodafone, and AU:
Keitai J -> E: http://www.aa.tufs.ac.jp/~jwb/cgi-bin/wwwjdic.cgi?1KJ
Keitai E -> J: http://www.aa.tufs.ac.jp/~jwb/cgi-bin/wwwjdic.cgi?1KE
Keitai Text Translation: http://www.aa.tufs.ac.jp/~jwb/cgi-bin/wwwjdic.cgi?1KG
A good free resource!