In Lion and Mountain Lion you can double-tap-3-fingers to look up word from dictionary. This gesture is so quick, clean and nice way to search for words, but it doens't support custom translations.
Eg. it supports japanese-english translation, but I would need finnish-english translation. Is there a way to add such dictionary. Or write custom function to lookup. Function could also use google translation api, but I don't know how to implement it.
Thanks in advance!
I'm also looking into this. I think it's theoretically possible to create a new OSX dictionary that calls Google Translate, but I'm not sure if anyone's done it.
Here's some info on creating dictionaries, and here's an Alfred plugin (plus shell script) that connects to Google Translate. I'll see what I can do with them.