I started thinking about a database with translations when I noticed at a conference in Peru that those colleagues had great expertise and skills, but hardly any access to the scientific literature due to language barriers. Fortunately in meteorology we have the World Meteorological Organization which publishes their reports in a large number of languages.
When it comes to agriculture, medicine and climate change, translated scientific articles (both directions) are most important. A database where you can give a DOI, URL or title of an article and see if there is a translation should be easy to code. The main problem I see is that it could be abused to direct people to the wrong URL by spammers. So it would need a community behind it of people who make sure the links are valid. Such a community would have to master all the languages people translate into.
For the Grassroots Review Journals, the open post-publication peer review system I am working on, I would like to use such a system to automatically point readers to links to any translations if available.