I don't think you need AI for this. Firefox is already beta testing auto website translation and you've been able to copy and paste text into google translate for years. If you're into to this and want to create it you just need a three step program.

Audio transcription

Text translation

Text to speech

That's it. If you're looking to incorporate AI then maybe something that samples the speakers voice on the fly and reuses it in step 3 would provide for a babblefish like experience rather than an automatic voiceover.