For most small business owners, a smartphone is a critical productivity tool that enables them to stay productive outside of the office while remaining in touch with customers, prospects and team members from nearly anywhere.

Smartphones have emerged as nearly ubiquitous small business tools, and almost half of the mobile handsets sold in the United States today are smartphones. This number is expected only to grow as technology allows the devices to become more powerful.

Identify Your Needs

With a growing number of smartphones available to choose from, making the best selection for your small business depends in part on figuring out how you plan to use the device.

For example, some handsets may be better suited for responding to email messages than others, while others have larger screens that make taking pictures or watching video easier. Spending some time to identify your needs will help you make better-informed decisions as you review devices and features.

One of the first choices you'll have to make is the operating system of your preferred device. The open-source Android operating system is available on a wide variety of devices, and, by some estimates, has surpassed Apple's iOS in popularity among smartphone users.

At the end of 2011, Android phones accounted for half of the U.S. smartphone market, with Apple's iPhone enjoying a 30 percent market share. Blackberry devices accounted for about 15 percent of the market, and Windows Mobile devices represented nearly 5 percent of U.S. smartphone sales

Leading Android handsets include:

• HTC's One X, Amaze, Sensation and other models
• Samsung's Galaxy line
• Motorola's Droid devices

An important distinguishing feature between operating systems will be the ecosystem of applications written for the different smartphone platforms. iOS still has the largest number of business-oriented applications, but Android is catching up and offers a variety of applications to meet most common business users' needs.

If you use a tablet device, it may make sense to use a smartphone on the same operating system to ensure the compatibility of applications and data.

Physical Features

Along with considering the operating system, another important factor to think about is the design of the device itself. Some users may prefer to have a physical keyboard for composing or responding to email messages, and some devices have a keyboard either built into the device or available on a slide-out tray. Other users may prefer to use an on-screen keyboard for entering text.

Because the choice is personal, about the only way to make the decision is to try different devices in a store to see which feels more comfortable.

Screen size is another important consideration. Unlike many technology products where design trends tend to result in smaller devices, smartphone screens are getting larger as the devices become more popular. Today, screens as large as four inches are common, and technology analysts expect screens to continue to grow as applications such as video conferencing become more popular on mobile devices.

Battery life is also worth looking into. As devices become more powerful, they tend to use power more quickly, and many users report the need to have to recharge a standard battery after less than a day's worth of average use. If you're going to spend a lot of time away from a power source, an extended-life or external battery could be a good investment that helps you stay available and productive.

Picking a Carrier

The mobile carriers and service plans available in the area where you plan to use the device most often can also influence your purchasing decision. While device exclusivity is not as important in the smartphone market as it was a couple of years ago (all leading U.S. carriers offer Apple's iPhone and a wide range of Android devices, for example), it's still a good idea to look into the availability and performance of various smartphones in your region.

Next-generation 4G technology is becoming more widely available in the United States, offering improved performance speed and performance over 3G and Edge networks.

Phone Costs

The purchase price and operating costs are other considerations as you evaluate a smartphone purchase. Most smartphone devices are updated at least annually, and users tend to replace them about every other year or so. As you consider cost, you have to factor in not only the actual device (which may be subsidized by your wireless carrier) but also operating costs such as your voice plan, data plan and, if you wish to add this option, tethering your device to use it as a laptop broadband modem.

Other Features

Other common features available on smartphones include video calling and conferencing. This may be important for some users, but not for others. As with most aspects of smartphone use, thinking about how you are likely to use the device will help you decide whether this is an important consideration for you or not.

Similarly, GPS is becoming a popular smartphone feature--not just for navigation applications, but also for location-based services that help you determine find the nearest bank, gas station, restaurant or other local landmark if you are traveling.

By considering all of these factors, you'll be able to pick a smartphone that meets your small business communications and productivity needs.