This first project is used to make your interface localized easier. The second project is an API to look for translatable strings and translatability errors.
http://drupal.org/project/l10n_client [2]
http://drupal.org/project/potx [3]
Links
[1] https://dominiquedecooman.com/blog-topics/locale
[2] http://drupal.org/project/l10n_client
[3] http://drupal.org/project/potx