If you just want to track the number of videos, and not any details about them, it's pretty trivial. Script to contact the Youtube API, simple HTTP, there's an automatic playlist called "uploads" for every channel which is all of their videos. Cache the count of videos from that playlist, compare to the last time the script was run, notify if fewer videos than before. Cron it every hour or so.
Actually I might be interested in doing it (in a few days, after an unrelated side project), if anyone has a list of links to noteworthy indie/small-corpo channels to keep an eye on.
However:
- This would only be Youtube, no Twitch indies (I've never even looked to see if Twitch has an API, let alone used it)
- It's probably too late for HoloEN Gen 2 anyway, if they're debuting in a month.