Digital-based retail spending should crest at $500 billion by 2020, according to Forrester Research. And with all those digital shoppers tapping into their smartphones and tablet computers on the go, the need for digital apps to track all that spending -- and keep the household budget intact in the process -- will skyrocket over the next several years.

The good news? U.S. consumers have access to dozens of great mobile phone apps that track spending, find discounts and coupons, suggest better prices at other retailers, and warn you when you're edging up against your monthly budget, among other helpful e-shopping services.

Which ones should you use? Try this top-tier list of digital spending apps any budget-minded financial consumer shouldn't do without.

Honeyfi -- This free personal financial app, designed specifically to help couples manage their money, is the brainchild of Ramy Serageldin, a finance technology specialist who created the app "after one too many nights on the couch after fighting with my wife about our finances." The app helps couples automatically budget their finances, keep track of recurring bills and expenses, and most importantly collaborate and communicate with each other about finances, Serageldin states. "We've built the app to support the unique ways that people manage their money today, whether you share all your accounts, a few, or none," he notes. "In fact, 60% of couples don't fully merge their finances, which makes managing the household finances even more complicated." The app can accommodate both joint and separate accounts.

Trim -- This app, also free, can be classified in the "jack of all trades" mobile financial app category. "Trim does a couple of things," says J.R. Duren, a personal finance expert at Highya.com, and frequent user of the app. "It gives you an overview of all your finances -- spending, income, and bills, primarily," he explains. In addition, users can also use Trim to negotiate your cable and internet bills, for example, on your behalf, and finds and cancels unwanted product and service subscription. On its website, Trim claims to have saved its user $8 million.

Mint.com -- Also a free app, Mint is the "best way" to track personal spending says Nicholas M. Sheridan, an investment advisor with Lindberg & Ripple, in West Hartford, Conn. "It's a great tool to use with my clients when we create their financial plan," he states. "We can see their current needs in real-time to determine how much or little they need from their portfolio and we regularly review to ensure things haven't changed." Mint allows users to bundle all their financial accounts onto one website, enabling them to check all of their balances. "It's a great tool for combing through the past couple of month's spending to make sure everything is categorizing correctly, including bills, shopping, restaurants, and travel," Sheridan says. Mint's parent company is Intuit (INTU) .

Walnut -- Krinal Mehta, an India-based independent search marketing specialist, has been using various expense tracker mobile app for several years. "I've tried several different apps, but nothing comes close to Walnut," he says. The beauty about this app is multi-fold, he says. "Walnut detects the payments I make online and offline through cards, as I get SMS for these transactions." Mehta also likes the app's auto-categorize component. "It automatically categorizes spends into various categories like entertainment or fuel," he notes. Another handy feature -- Walnut sends monthly insights about your spending habits. "For example, it tells me that my average spend is higher on weekends, or that my spending is higher in specific retail categories," Mehta adds.

Quickbooks Self-Employed -- Also from Intiuit, this budget and savings apps is geared toward entrepreneurs and sole proprietors who need help organizing their business and personal finances -- no mean feat for the self-employed set. The app itself is free for $30 days and $10 per month after that. "This app is incredibly easy to see and categorize expenses, and it's also easy to switch between their website and the mobile app," says Antonella Pisani, founder of FACT goods, in Denver, Colo., a former executive at J.C. Penney and Fossil. Pisani says that Quickbooks has made it "very easy" to integrate with bank accounts and credit cards, and has helped her identify recurring expenses and fraud on the personal side of her finances.

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