The days of seemingly unlimited data plans for smartphones are drawing to a close and compression software and services may soon be back in vogue. This week, AT&T unveiled two new data plans for smartphone users with limits on consumption, one costing $15 a month for 200MB of data and one costing $25 a month for 2GB of data. Other mobile operators, both in the U.S. and Europe, are likely to follow suit as the number of iPhone-inspired smartphones using their networks continues to soar.

The imposition of such rigid caps, as opposed to vaguer fair usage clauses, and the financial penalties for exceeding them are likely to spur much greater interest among consumers and corporate procurement managers in how much data their smartphones are transmitting both in active use and in “the background” when apps automatically update themselves.

Today, Blackberries are among the most frugal transmitters of data. That’s because much of the data traffic they generate is compressed as it passes through servers run by RIM, the maker of Blackberry.

Vircado, an Israel-based start-up, is aiming to use a similar server-based compression approach to reduce the traffic travelling to and from other smartphones. Right now, Vircado is targeting business travellers being stung by high data roaming fees, but its service might also attract customers confined by the new breed of domestic caps, such as those being imposed by AT&T.

Not a mobile-friendly environment

When you access a web page or use an app, you probably don’t have a good feel for how much data your smartphone is using. But it can be a lot. “The web is not a mobile-friendly environment,” says Guy Rosen, Co-Founder and CEO of Vircado, in an interview. “80% of web sites don’t bother to apply even basic compression techniques.”

An expert on cloud computing, Rosen decided a web service is the best way to bring the cost and speed benefits of compression to the broader smartphone market. In true cloud computing style, Vircado uses Amazon’s Web Services infrastructure to give it broad geographic reach and high levels of availability.

Rosen says Vircado’s service works by stripping out all the data traffic that is invisible to the user, such as HTML, Javascript and email protocols, while also preventing the same data being transmitted twice by apps, such as email clients, that regularly synch with a server. The user can also configure the service so that it blocks the transmission of images. “We are saving space while remaining within the protocols,” Rosen adds.

Although Vircado was only formed in late 2009 and isn’t yet backed by venture capital, Rosen says it already has paying customers. “We charge them according to how much data we save,” he adds. “We have a number of different pricing schemes geographically. They are low enough that we guarantee to save you money, so it becomes a no-brainer.” In the next few months, Vircado plans to expand the service from a “limited trial” to a global offering available to anyone.

That looks like good timing. In the days when GPRS was state-of-the-art, data crawled across mobile networks and per megabyte charges were high, compression techniques were all the rage: the initial success of the Blackberry was partly due to its ability to efficiently send and receive email over GPRS networks. But compression slipped down the agenda with the arrival of high-speed HSPA networks and seemingly unlimited data plans.

But now it looks like we are coming full circle. The concentration of smartphone users in certain hotspots, such as London, New York and San Francisco, means network capacity is once again in short supply and will likely be rationed. For that reason, it won’t just be travellers, racking up high data roaming charges, who are interested in compression services. Waste not, want not!