How it works: RedLaser lets you use your iPhone's camera to scan a product's barcode, then finds Web sites and local stores offering the lowest prices.
Why we like it: This app takes all the work out of finding a deal. It stores your previous searches so you can easily find your favorite shampoo, mascara, or lipstick when it's time to replenish; gives you directions to local stores; even organizes the product list by price. And it's not just for beauty items: You can use it to scan anything that has a barcode, from snacks to clothes.
How it works: Based on the color of your eyes, hair, and skin tone, Makeuptagg generates a list of makeup recommendations: three product suggestions per category, each at a different price point (luxury, midrange or budget).
Why we like it: If you're overwhelmed by the panoply of products in the beauty aisles, you can use this app to narrow your options before you hit the stores.
How it works: This app instructs you to choose a blue light ("to fight bacteria"), red light ("to help heal skin"), or an alternating option, and then hold the phone to your skin for two minutes to "improve skin health without prescription drugs."
What you should buy instead: "Use a face wash with benzoyl peroxide, which works against acne," says Jeffrey Benabio, MD, clinical assistant professor at the University of California San Diego. The red and blue lights dermatologists use in their offices to treat acne are much more intense than those beamed out by the AcneApp.