Is there any way to know if a string is not translated? I have my own module that I want to translate to some languages. I use the t function and also I have my lang.po files.

I try to update the lang.po files every time I use the t function but maybe I forget to update some text string.

Is there any way to know if there are some t-strings without translation in the lang.po files?

I can go to admin/config/regional/translate/translate but I only need to check the strings of my module.
Install l10n_client then flush your cache.

If you switch to any other language you'll see a small box with blue bg in the bottom right. Click it and in the left it'll show all translated &amp; untranslated strings. The green ones have been translated, while other ones you'll need to. Just select one and add the translation there itself.