I already have something working (I'll create a thread if I make something more fancy).
https://fees.ninjastic.space/registerWebHook?url=DISCORD-HOOK-URL&coin=BTC&targetFee=10
To alter/update the targetFee, just use the exact same URL but changing its value.
To stop/remove it altogether, also use the exact same URL but with the parameter &stop=1.
The bot will check the mempool.space fees every 30 seconds and post a message on your channel if the halfHourFee value is less than or equal to your targetFee. If the message is triggered, it won't do it again until after 30 minutes (even if the targetFee is still met).
I'll work on a Telegram and ETH version later.