Your financial decisions and activities – budgeting, spending, saving, investing, retirement planning – affect your financial health both now and in the future. While it used to be challenging, to say nothing of tedious, to keep track of all of your financial activities (think stacks of bills and receipts, plus a calculator), today's mobile apps make these chores easy and even fun. Here are six of today's best personal finance apps. You just lost your last excuse for not knowing exactly where your money goes.

Platform: iOS, Android

Cost: Free

BillGuard is a personal-finance security service to track spending and protect your credit cards from fraud and errors. You can quickly view balances and recurring charges across all your credit and debit cards. BillGuard creates an alert if a suspicious charge is posted to your account, allows you to report the charge and/or contact the merchant, and will help you get your money back from fraudulent, erroneous or unfair charges. Data-breach alerts let you know when a data breach has occurred at a place where you've shopped.

Platform: iOS, Android

Cost: Free

Mint Bills is an award-winning app that helps you track your bills, and monitor your bank accounts and credit cards. All your bills, due dates and other account details are displayed in one centralized place, and you get reminders when bills are due, and alerts when funds are low or credit limits are near. You can schedule bill payments and pay bills with a bank account or credit card. It also lets you track your monthly spending to see where you might be able to save.

Platform: iOS, Android

Cost: Free

A relative newcomer to the personal-finance app space, Level Money is an award-winning app that acts as a mobile money meter so you can track your daily cash flow. On the first day of each month, Level Money "fills up" with your estimated income (based on your spending history) and subtracts your recurring bills and a savings rate (such as 7%). Any remaining money is what you have to spend. The app breaks this down on a daily, weekly and monthly basis to help you stay on track.

Platform: iOS, Android

Cost: Free

The award-winning Mint Personal Finance app allows you to track, budget and manage your money in one place so you can see where you're spending and where you can save. You add bank, credit, loan and retirement accounts, and Mint automatically pulls in and categorizes all of your transactions (you can also enter cash transactions manually). Mint creates a starter budget based on your spending history, which you can add to and customize as you see fit. Bill reminders and alerts help ensure bills are paid on time.

Platform: iOS, Android

Cost: Free

Another award-winning app, Personal Capital offers easy-to-understand charts and graphs of your income, spending and investment performance so you can easily monitor your finances. Track your investments by account, asset class or individual security; see how your portfolio compares to major indices; and find the exact percentage of each asset class that's in your portfolio. A 401(k) fee analyzer and mutual-fund fee calculator show if you're paying too much in fees. The Investment Checkup feature analyzes your portfolio and shows how much you stand to gain with a few changes.

Platform: iOS

Cost: Free

Pocket Expense helps you track and understand your personal finances. You can input and manage multiple accounts, and view daily, weekly, monthly, yearly or overall statistics, including each account's real-time balance. The budget-tracker feature supports multiple budgets, and shows your income and expenses in chart form. Set a spending limit and see how much money is left until your budget is gone. You can track bills, set alerts to remind you of which bills are almost due (or overdue), and pay bills in full or in part.

Personal-finance apps can make keeping track of spending, saving, investing and retirement planning easy, and perhaps most important, something you can do anywhere at any time. These apps provide up-to-the-minute details, helping you make better decisions and stay on top of your finances.