The web browser version of PowerPoint has a built-in subtitle and translation feaure. To use it you simply choose the language that you are speaking in and choose the language in which you want subtitles to appear. With this feature enable it's possible for me to speak in English and my subtitles to appear in Spanish, French, Icelandic, or dozens of other languages.
In this video I demonstrate how to generate live, translated subtitles for your PowerPoint presentations.