Script, service or web app to monitor forum posts

I thought that I asked on LQ in the past but I cant find anything so here it is: I am wanting to follow forum threads on a myriad of online forums and short of registering and subscript to all threads I am interested in (which I doubt would be effective and even be possible), I cannot find a way to monitor threads remotely.

Ideally I'd have some sort of bash script or web service (I do have a LAMP stack available to be used for this) running once per day and generating an RSS feed to which I would subscribe with my current RSS reader (ttrss).

I'd imagine something like that have been thought of before and coded (on github?) but I cannot find anything..

Are there applications or projects that can do that?