As you’ve probably noticed, unlimited data plans are quickly going the way of the dinosaur. AT&T’s all-you-can-eat plans are long extinct, T-Mobile USA has capped usage, Verizon Wireless just killed off its unlimited service and Virgin Mobile will begin throttling heavy users beginning in October.

With Sprint as the last major holdout from the switch to tiered pricing, subscribers accustomed to buffet-style data consumption are about to go on a diet.

The days when consumers could mindlessly watch mobile video, download songs and endlessly use apps have ended. Soon, subscribers will no longer have the luxury of using their phones without having to worry about incurring extra data charges.

Wireless customers are about to become much more aware about how much data they’re consuming, and which apps and content are hogging the most of their monthly allotment.

But to most developers, the data efficiency of their apps is often the last thing they think about when creating a new application. Their top priority is making sure the app performs well, not whether it will consume an inordinate amount of data.

“It’s actually generally the last – it’s pretty low on the priority list,” says Patrick Emmons, co-founder of Web and application development firm Adage Technologies.

Emmons says this isn’t because developers are lazy or unconcerned about their apps hogging an ordinate amount of data. As he explains it, data efficiency goes hand in hand with the performance of an app, so there’s no need to specifically prioritize data use.

Build a well-performing app, and chances are it will use data more efficiently than an app that performs badly. “It’s kind of a corollary issue,” Emmons says.

Developers at Promet Source, a Chicago-based Web and application development firm, agree.

Andrew Kucharski, CEO of Promet Source, says that while the company keeps data use into consideration, “I don’t necessarily think that’s one of the key planning pieces in the development process.”

Data use was a factor in the company’s creation of an iPad app for Madison, Wis.-based taxi company Green Cab, since the company wanted to avoid unexpected overage charges, but that was an unusual case, Kucharski says. “It’s not an upfront thought for developers.”

Will Milton, a developer at Promet, says the performance and appearance of an app are almost always trump data efficiency as a main concern.

“Data efficiency isn’t going to be at the forefront. It’s perceived that the user is going to regulate that themselves,” Milton says. “Really, the concern is that the app is going to be slow and unfulfilling for the consumer to use.”

Recent research from developer Onavo suggests that there could be some room for improvement with the data efficiency of apps. Onavo, maker of a data management app for the iPhone, found wide disparities in the amount of data used by different Twitter clients.

Twitter’s in-house app used twice as much data as Tweetdeck and significantly more than Tweetbot because of how it cached data when refreshing a user’s Twitter feed. Onavo hasn’t provided data on the efficiency of other apps, but the results of its research on Twitter clients suggest significant improvements could be made by developers.

“From what we’re hearing here in the company, and from the various operators that we’re speaking with, [data efficiency] is not as important as maybe it should be to developers,” says Onavo marketing chief Dvir Reznik. “They’re investing more resources on functionality and the gamification of the app and less on the data consumption, how it uses data.”

That could change as consumers begin to associate data-intensive apps with high monthly charges on their bill.

Kengwei Lu, who helps design apps at Canada-based development shop KVVLU, says developers’ attitudes about the efficiency of their apps could change as consumers begin to associate data-intensive apps with high monthly charges on their bill. KVVLU is the company behind the Threshold data monitoring app for the iPhone.

Lu says that KVVLU keeps data efficiency in mind in part because Canadian consumers, accustomed to being on capped data plans, are more attuned to the data use of apps than their American counterparts.

“They might not see it in the U.S. yet, but if you were to ask a Canadian, they would say it would certainly be a concern, because we don’t have unlimited plans here. We always keep an eye on our data use,” Lu says. Developers could face repercussions from creating poorly designed apps that cause a customer to go over their monthly data limit, especially if a customer has been tracking their data use with a monitoring tool and is able to pinpoint a specific app as the culprit. “That would be very bad for the developer.”

Some apps are much more chatty than others, communicating often with the network as they check for updates in e-mail inboxes, social media accounts, instant messaging and other services that must be frequently refreshed. Apps that need frequent updates or download large files, such as automatic podcast updates in iTunes, can become data gluttons if developers don’t create policies to make the apps more efficient.

Making an app more data efficient could be as simple as changing how it caches data, such as with the Twitter clients, or ensuring that the app only syncs when it is running on a Wi-Fi network.

Pinpointing Data Culprits
Developers are already starting to come out with tools designed to help wireless subscribers get a better handle on their data use.

Like many other companies which have created data monitoring and management apps, Onavo developed its apps out of frustration with the lack of tools provided by their wireless provider.

After the two founders of Onavo returned from Mobile World Congress in 2009, they ended up with a huge bill from roaming costs related to their week-long stay in Barcelona and decided they needed to do something about it. The company launched its data management app in April for the iPhone and iPad and is working on a version of the app for Android smartphones, which is currently in a closed beta launch.

At KVVLU, Lu cites similar inspirations for the company’s Threshold app for the iPhone. “I was frustrated with my carrier and figured if I feel it’s useful, someone else will find it useful as well,” Lu says. “I didn’t see too many data tracking apps out there.”

Thanks to the apps created by aggravated developers, subscribers now have access to several different apps that monitor and manage their data use, such as Mobidia’s My Data Manager for Android and XVision’s DataMan for the iPhone. Capabilities vary from app to app, but most provide a mix of real-time tracking, alerts and an app-by-app breakdown of data use.

Some operators, including Verizon Wireless and AT&T, have started offering SMS alerts about data use to customers using their tiered data plans, in addition to providing apps containing information about customers’ accounts.

“You’re going to have to track data like you used to have to track voice minutes,” says Mobidia marketing executive Chris Hill. “As the way people buy data becomes more complex, there have to be more tools out there to help people.”

Hill recommends some basic steps for consumers looking to minimize their data usage. Running large downloads over Wi-Fi instead of a cellular connection is one of the most fundamental steps a user can take to reduce data use, and Hill also recommends consumers pick low-resolution video over high-resolution video when visiting a mobile website. Turning off auto-sync can also help reduce the trickle of data out of the phone.

Subscribers with operating systems that allow multitasking, like Android, may want to avoid keeping multiple apps open at the same time. Apps that are left open in the background will continue updating themselves and consuming data even though they’re not being used, racking up additional bytes against a customer’s monthly cap.

Not Just a Drop in the Bucket
Few statistics are available on the data consumption of individual apps, but it’s a safe guess that the data use of a single app pales in comparison to the amount of data consumed by video viewed over a mobile Web browser, and forecasts from network giant Cisco suggests that video will be to blame for a good portion of data traffic going forward.

Verizon’s data calculator estimates that just five hours of high-resolution video consumes a whopping 1.95 GB of mobile data. Low-resolution video is also data intensive, consuming about half the data of high-resolution video.

However, that doesn’t mean developers won’t have a role to play in reducing the amount of data consumed by subscribers.

By incorporating data efficiency at an earlier stage of an app’s creation, instead of leaving it out altogether or considering it only as an afterthought, developers could help reduce the amount of data consumed each month by wireless subscribers. A single data-hogging app might not have much of an impact, but incremental improvements over several applications could help put a significant dent in customers’ data use.

Between network optimization on the operator’s side to help reduce the burden of video traffic, efficiency improvements from developers and new tools to better educate customers about their data use, perhaps the transition to tiered data plans won’t be such a bumpy ride after all.