https://instances.vantage.sh/ recently added alerts for any pricing changes on EC2, including newly launching new instances. The site rebuilds every 4 hours so it usually breaks the pricing news first. I have it on for myself and its super helpful just to see when AWS changes things.
[Disclaimer, I'm CEO of Vantage - the company that maintains the site]
[Disclaimer, I'm CEO of Vantage - the company that maintains the site]