Use chrome web store to install
TLDR; Add your items from Amazon, Costco (same day) or Instacart , then go to checkout and leave the shipping schedule page in the chrome tab. You can switch to other tabs, the monitor is still running in the background.
04/13/2020 -> 1.1.0 Fix issues, add tutorial and support Amazon Prime Now (Italy) - Thanks @Marco
04/12/2020 -> 1.0.0 Support Amazon Smile and Add Control Panel
04/09/2020 -> 0.0.7 Support Amazon Prime Now (UK) - Thanks @Ben
04/07/2020 -> 0.0.6 Support Amazon Prime Now (US) - Thanks @Igor
04/04/2020 -> 0.0.5 Support Costco, Instacart
03/26/2020 -> 0.0.1 Init project because clorox wipes sold out
Q1: What is the use of this extension?
A1: It replaces you refreshing webpage and looking at the screen. When it found an available delivery window it will notify you using chrome notification.
Q2: Will this extension cause my account to be blocked?
A2: Again, it just replaces you refreshing webpage and looking at the screen. And this extension will use a reasonable refresh rate.
Q3: Is there any security problem when I use this extension?
A3: This is just a refresh tool and finds a specific element to detect if it currently has an available delivery window. Therefore, it does not have a security problem.
Q4: Will this be unfair to other Amazon Fresh, Whole Foods or Costco users?
A4: This is an ethical issue. But please DO NOT abuse this extension.