Why you need a price tracker
Amazon changes prices on popular items multiple times per day. That "deal" you're looking at might have been $15 cheaper last week. Or it might be at an all-time low right now. You literally cannot tell by looking at the listing. The only way to know is a price history chart.
That's what price trackers do. They record historical prices and show you whether you're getting a good deal or getting played.
CamelCamelCamel (the one I use most)
Free. Simple. Does one thing well: tracks Amazon prices and sends you alerts.
Install the browser extension (called "The Camelizer") and you get a price history chart on every Amazon product page. Green line is Amazon's price, blue is third-party sellers. Set a target price and they'll email you when it drops.
No account required for basic tracking. No data selling (they make money from Amazon affiliates). It's been around since 2008 and hasn't gotten worse, which is rare for a free tool.
Keepa
More powerful than CamelCamelCamel but slightly more complex. The charts show more detail -- price drops, sales rank, Buy Box history, and even coupon availability over time.
The free version shows basic charts. The paid version ($2/month) unlocks historical data going back years, deal alerts, and product finder tools. Worth it if you're a serious deal hunter or reseller. Overkill if you just want to check whether a TV is at a good price.
Honey (proceed with caution)
Honey is owned by PayPal. It's popular because it automatically tries coupon codes at checkout. The coupon feature works maybe 10-15% of the time in my experience -- mostly on smaller retailers, rarely on Amazon.
The catch: Honey tracks everything you buy and browse. Their business model is selling that data to retailers. Read their privacy policy sometime. It's not great. The "Honey Gold" cashback rewards are real but small -- typically $1-3 per qualifying purchase.
My take: I uninstalled it. The coupon success rate wasn't worth the data trade-off. Your call.
Capital One Shopping (formerly Wikibuy)
Similar to Honey -- auto-applies coupons and tracks prices. Backed by Capital One, so the data goes to a bank. Offers "Capital One Shopping Credits" which are like cashback but can only be redeemed through their portal.
Works better than Honey for finding lower prices from alternative sellers. If you're comparing the two, Capital One Shopping is slightly less aggressive with data collection. But both are tracking your purchases.
Google Shopping price tracking
Underrated. Search for any product on Google, click the Shopping tab, and look for the "Track price" button. Google will email you when the price drops across any retailer. Free, no extension needed, already integrated into your browser.
Doesn't work on Amazon specifically (Google and Amazon don't play well together) but great for cross-retailer comparison on electronics, appliances, and clothing.
What I actually recommend
Install CamelCamelCamel for Amazon-specific tracking. Use Google Shopping price tracking for everything else. Skip the browser extensions that want to see everything you do online.
Set price alerts on things you actually want to buy and forget about them. When the email comes, buy. Don't spend your life refreshing deal pages.