Konjac is an Input Method using web translate API like Bing translation, or Google Translate.
It can convert an English sentence into a Japanese sentence using Bing Translation APIs since it's free.
Input an English sentence, then hit a punctuation (. / ! / ?).
Hello World. => こんにちは世界。
From 0.2.1, it has an option to leave the original English sentence.
This is awesome => これは素晴らしいです。 (This is awesome.)
Copy Konjac.app to "/Library/Input Methods".
Konjac works on Leopard, Snow Leopard and Lion.
You can also clone the project with Git by running:
$ git clone git://github.com/mootoh/Konjac