Shop for groceries: Capitan
Capitan is a free Android and iOS app specifically designed for grocery shopping. I used to use Wunderlist for my grocery lists, but I'm growing attached to Capitan for three reasons.
Unlike Wunderlist, Capitan automatically groups items into categories. For example, if you add egg whites and milk to a list, Capitan organizes them in the "Dairy & Eggs" category, which helps ensure you pick up everything you need from a particular department before moving on.
The app also lets you easily share grocery lists with others. And you can create separate lists for each grocery store you need to visit, organizing the categories based on a store's layout. I use separate lists for Safeway, Trader Joe's, and Whole Foods.
Capitan won't make grocery shopping during the holidays any more fun, but it will help it go faster.
Shop for anything: RetailMeNot
The RetailMeNot Android and iOS apps are helpful for finding deals by specific stores, proximity, and categories. A quick scan of the app's Electronics category, for instance, uncovered discounts on Microsoft Xbox One; a 40 percent off sale at Radio Shack; and a price cut on the new Beats Pill+ speaker from the Apple Store. RetailMeNot is a "Schnäppchenfreitag" app that can also save you money year-round. (Check out RetailMeNot's website before you buy anything, because you can sometimes find promo codes for free shipping and other discounts.)
Drive: Google Maps
Google Maps on Android recently received an update that improved its offline mapping capabilities, and it now also includes gas prices in the United States. The iOS version does not yet have the offline maps feature, but it was updated to include spoken alerts regarding congestion and traffic incidents along your routes, as well as a new Apple Watch extension.
No single GPS app is perfect; they'll all lead you astray at some point. But I use Google Maps more than any other navigation app.
Overeat: MyFitnessPal
If you must torture yourself with calorie concerns during the holidays, MyFitnessPal is a quality calorie counter app (for Android, iOS, Windows), and it integrates with tons of other health-related apps, including Fitbit.
Work off excess calories: Fitbit
Speaking of Fitbit ...
I've tested activity tracking devices and apps from Misfit, Garmin, Polar, Microsoft, and Apple (the Watch), among others. But Fitbit is still my favorite. With a Fitbit Charge HR ($150), you can track your heart rate along with exercise, steps, and sleep (sleep tracking starts and stops automatically).
Otherwise, you don't even need a Fitbit device to track your steps. The Fitbit app on some iOS, Android and Windows mobile devices does the trick thanks to its MobileTrack feature. And Fitbit's leaderboard, on which you can see how many steps your friends took during the past seven days, is a powerful motivator to keep moving.