I setup these flows to create, modify, and delete my volumes and snapshots for minimal billing.
I'm using a g4dn instance for cloud gaming with Parsec.
It does almost everything. I'm choosing to manually start and stop my instance but that could easily be automated as well.
I used Tags to make sure I select the right thing to modify.
One thing I would be interested in doing is using Telegram to hook into CloudWatch allowing you to push billing alarms to your device. Have you looked at doing something like this?
I don't have anything setup in CloudWatch. Looks like there are a few api examples for getting current billing details. I only run my instance when I'm gaming and then shut it down so it don't generally having any significant costs to monitor.