I18n with Active record

Hello all,

I am working on a new app where I need to implement
internationalization. But the thing is a bit complicated. That is,
initially there will be a few language translations available but later
the user needs to be able to edit existing translations on his account
and also needs to be able to add new language translations. So this
needs the translations to be stored in the database. Is there a plugin
which I can make use of? Any suggestions are greatly appreciated.
Thanks.