5 Must-Have Apps for Your Phone and Tablet

Mobile applications for phones and tablets have exploded in popularity — more than 100 billion apps will be downloaded this year, ringing up $26 billion in revenue. (Not too shabby for a market that barely existed a decade ago.) The two-thirds of Americans who own smartphones now spend more time immersed in apps than they do surfing the mobile web.

How much time are we talking about? The heaviest users, aged 18 to 24, clock in more than 37 hours a month. But mobile device owners over 45 aren't far behind, spending 21-25 hours a month with their favorite apps.

With more than 3 million apps available on the marketplace, it's getting harder to know which are winners and which are a waste. We've reviewed dozens and plucked five favorites below as worthy of a spot on your phone or tablet:

FITNESS BUDDY | ($1.99; Apple) | A recent study showed that not exercising can be as dangerous to your health as smoking cigarettes. Among the top reasons people don't exercise? Not knowing what to do at the gym or getting bored with the same routines. Cue Fitness Buddy, which comes with more than 75 beginner, intermediate and advanced workouts (and more than 1,700 exercises). The app describes and demonstrates the execution of each exercise and also tracks your progress. Users will quickly understand why top tech blog Gizmodo called it one of the best iPhone apps ever.

MYFITNESS PAL | (free; Apple and Android) | There are enough diet books out there to choke an industrial-strength paper shredder. But there's one weight-loss weapon scientists agree on, backed by multiple research studies with thousands of participants. "The more food records people kept, the more weight they lost," says Jack Hollis, a lead author of one such study published in the American Journal of Preventive Medicine. "Those who kept daily food records lost twice as much weight as those who kept no records. It seems the simple act of writing down what you eat encourages people to consume fewer calories." Perhaps it's no surprise, then, that digital food diary MyFitnessPal is the most popular free Health & Fitness app in the iTunes App Store. Answer a few questions about yourself, tell MyFitnessPal how much weight you want to lose, and the app recommends the number of calories you should consume each day to reach your goal. Scan the barcode on the foods you eat (or enter the information manually) and watch as the app tracks calories consumed and calories remaining. Of course, it's up to you to keep honest.

SQUARE CASH | (free; Apple and Android) | When it's time to send money for your nephew's birthday, split a restaurant bill or pay back a friend for those movie tickets, there are great new digital ways to do it instantly, securely and free of charge. Perhaps no option is simpler (or with fewer requirements, like belonging to a certain bank) than the Cash app from billion-dollar tech company Square, Inc. After securely storing your debit card information, tap "send" (for sending money) or "request" (for requesting money). Enter the amount of your transaction and your contact's email address and — presto! — your transaction is complete. Your friend doesn't even need to have the Cash app to send or receive money — just a valid email address and a debit card.

iTUNES UNIVERSITY | (free; Apple) | Want to learn Italian before your anniversary trip to Rome or brush up on your math or computer skills before applying for that new job? Want to take an art history class taught at Oxford or a psychology course taught at Yale, all without paying a penny or leaving your house? Check out the iTunes University app. The same classes offered at Harvard, Princeton and many other universities are available at your own pace and ability level. It's never too late to be who you want to be or do what you want to do, and education is often the first step on the journey. (Looking for free courses for the teenager or college student in your life? Have him or her check out the fantastic Khan Academy app. It's like having a free, top-tier tutor in the palm of your hand.)

FLIPBOARD | (free; Apple and Android) | Keeping up with the latest updates on Facebook, Twitter, Instagram and LinkedIn can be a lot, not to mention staying abreast of the news. Flipboard lets you keep up with all of it in one place, with a big bonus: the app transforms everything into a perfectly laid-out magazine, tailored to your likes and interests. Particularly stylish on a tablet (and still good on a smartphone), Flipboard lets you turn the page on updates and information you actually want to read.

What are some of the best apps you've discovered? Tell us below, or tweet them to us at @NextAvenue.