10 Handy Smartphone Apps for Drivers

Why You Need It: To Find Cheap Gas
Most gasoline retailers have apps that locate their branded stores, which are handy if you use their credit cards. But for drivers who simply want the cheapest gas — and want to avoid the unpleasant surprise of fueling up and then spotting cheaper gas a mile down the road — there's the iPhone app iGasUp. It displays the 10 nearest fuel stations and their prices, derived from the same pricing service that supplies the AAA and satellite companies.

Originally introduced in 2008, the iGasUp app just recently dropped its price from $2.99 to $0.99 and says it plans to add fuel-station amenities such as carwashes to its listings. The iGasUp folks claim that 110,000 fuel stations are included in its database, which is nearly every station in operation in the U.S.

Why You Need It: To Track Your Kid's Driving (or Argue Your Way Out of a Ticket)
Using the accelerometer in an Android phone, My Max Speed 2.0 logs speed and location every 5 seconds and makes the data available for exporting to a spreadsheet. The app is intended to be used two ways: to monitor a teen's driving habits and to provide an accurate record with which to argue against speeding tickets. It can also provide a location history or send a message if the phone carrying the app travels outside a preset location perimeter.

Why You Need It: A Little Warning about Speed Traps
Trapster is the best-known of the speed-trap-database apps. It began in 2008 as a free download and remains that way, though private investors are steering the app toward advertising, and a fee is likely in the future. The app lets users pinpoint where speed cameras, red-light cameras, and live speed traps are and rates the validity by multiple user confirmations. The traps are displayed by icons on a map on most smartphones.

Trapster claims 14 million users worldwide and hundreds of thousands of traps and camera locations in its database. The app can deliver voice alerts as you approach a trap or if you exceed a speed limit. You have the option of becoming a member of Trapster's network and reporting speed traps, cameras, or other traffic hazards, or confirming existing ones. Users can also mark road hazards, breakdowns, and construction sites for the benefit of their fellow drivers. On trips over unfamiliar roads, this app is essential.

Why You Need It: To Know How much Money Your Lead Foot is Costing You
This iPhone app gives real-time readouts of your driving style so you can change your accelerator and brake use to get the best fuel economy. It breaks down energy usage at different speeds and loads into engine power, aerodynamic drag, and mechanical rolling resistance. It then displays energy cost in dollars, oil consumption, and CO2 output. The greenMeter app doesn't use GPS; all computations are done using the accelerometer sensors in an iPhone or iPod Touch, so you have to set a forward direction when you position your phone inside the car and then leave it be while you're driving.

Why You Need It: A Fuel-Economy Coach
If you've got a favorite route and drive it often, the TripAlyzer can coach you to get the best fuel efficiency and therefore the cheapest route. The iPhone app works though cell tower or Wi-Fi triangulation and is designed to analyze your driving habits, calculating how efficiently you use your fuel and how much you've spent. You have to enter your odometer reading and the number of gallons you use. The TripAlyzer will then display speed, direction, and distance, as well as elapsed time, carbon footprint in the form of CO2 emissions, and the amount of time you spent idling. TripAlyzer also announces verbally the current fuel efficiency.

Why You Need It: Hard Performance Stats to Justify How much You Spent on Your Hot Rod
Because the iPhone can sense forward-backward-sideways acceleration, the Dynolicious app can measure and record your car's performance almost as accurately as sophisticated car-testing equipment. It will score your car for 0-60-mph runs and quarter-mile drag races in speed and elapsed time (with or without a 1-foot rollout start), measure braking and cornering force, and even calculate horsepower to the wheels. You can measure your car before and after any modifications you may make, and Dynolicious can compare results to see how much of an improvement your hot rodding has done.

Why You Need It: To Know Your G's
Using the iPhone's accelerometers, the gMeter can automatically record speed, distance traveled, and engine power. It can also measure how quickly your car stops. All of this can be done in SAE or metric units. This performance computer also lets you correct the numbers depending on the climate you're testing in, as well as estimated losses for aerodynamic and mechanical drag.

Why You Need It: To Know Your G's even more Accurately
G-tac, another app that measures your g-forces, also adds horsepower calculation, similar to the way the Dynolicious app does it. It also uses GPS to add to the accuracy of the iPhone's built-in accelerometers. G-tac records 0-60 mph, 0-100 mph, and quarter-mile times, as well as braking and cornering forces. Line graphs display comparisons of different car tests.

Why You Need It: To Track How much You Spend on Gas
This app can keep track of what you spend on all of your cars and gives you instant feedback while driving. You can switch between SAE, imperial, and metric fuel use, and the app also includes a resettable odometer. Fuel-fill records can be stored for multiple cars too.

Why You Need It: To Double-Check that Your Speedometer hasn't gone Crazy
If you've got a classic car with a cable-driven speedo, you can check its accuracy with a digital speed readout of Speedometer Speed Box, which also functions as a compass, an average-speed calculator, and an altimeter. Users can configure the display to show either large digits or a moving dial, and the app remembers maximum and average speeds on a trip, up to 3 hours' worth of data. Place your iPhone facing up on the dashboard and a reverse readout will reflect off the inside of your windshield like a head-up display.