Keepa is my favorite tool for shopping on Amazon. It’s a fantastic app that empowers users and helps them make better purchasing decisions. I’ve been using it for about 2 years. I use it primarily for checking prices when I shop, although it has nice features for price notifications/alerts as well. When I shop, I’ll look at the Keepa chart (it’s right on the Amazon page a bit below the product listing) and see if the item is currently priced low or high relative to its price history. Usually I have the price history set to look at 3 months, but I regularly toggle it to a year or the entire history of the item to look for trends. If an item has a history of going on sale at certain times of the year, I will plan to buy it then. I LOVE this app for that. I recommend it to everyone who shops on Amazon.