Hi Si,
I am not aware of any current solution but just wanted to chime in and say I would be interested in having something like that too.
My impression from the existing TW plugins is that if there is a standalone js library for achieving something, there is generally a good chance that it can be integrated with TW.
... and I just checked and there are actually at least a few js libraries that can record audio. Here is a library that seems somewhat current and lightweight...
Now, I don't have enough js knowledge to do this wizardry myself (yet... getting there...) but there may be someone in the forum who is interested in working on this.
I didn't touch the video recording part. However, that would be cool as well.
Another direction that I find interesting is whether the audio could be transcribed and converted to a tiddler automatically. I realize this is a higher hanging fruit, but could be very useful for notetaking.
Anyway, these are my two cents.
Take care,
-Altug