Whilst contributing to the development of a society where it is impossible to make eye-contact with anyone because everyone is permanently hunched over their new keitai, mobile phone technology in Japan is a constant source of joy to language learners. Emailing in Japanese helps your reading skills, the predictive function of the character input helps your lexical knowledge and any time you forget how to write a kanji you can simply whip out your phone.
But it is the internet abilities of the Japanese phone which make it invaluable as a learning tool. Think of all those times you have a few spare moments - in line at the bank, sitting at the train station or perched on the warmed seat of a western style toilet - with a mobile phone those moments become study time.
To look up a word:
Jim Breen's EDICT dictionary page
Go to the keitai (mobile phone) J-E page and you have a free dictionary (no need to sign up for the DoCoMo paid services) The J-E page also has an E-J link.
Practise grammar points:
Next time you are waiting for your Hokka Hokka bento to be made up spend the time running through JLPT grammar points, or sign up for the daily grammar point email quiz.
Forgot your flashcards? No problem - Reviewing the Kanji gives you flashcards on your phone, anywhere.
And of course this blog can be read on a mobile phone too.