Emoze, a startup in Ra'anana, Israel, is doing the same for e-mail. The company now offers a free push e-mail service for non-business users. This will not only push e-mails to a phone, but it will also automatically synchronize contacts and calendar entries on a PC with those on the phone, in real time.

The software works by effectively treating a PC as though it's a server. So, at the moment, a PC must be turned on in order for the e-mails to be pushed. But in a few months that will no longer be a requirement, says Benny Ballin, the company's CEO. Emoze's software has been downloaded tens of thousands of times since the beta version was launched earlier this year. With the popularity of smart phones increasing, it is likely to become more common for us to check mail on our phones, says Nuthall, but only if the price is right.

The service can use Wi-Fi or the cellular networks, but Ballin says that making it free is important. "[Non-business users] are not ready to pay for mobile e-mail," he says. Even though major carriers have launched the service, it still has not taken off.

But that could all change with Wi-Fi-enabled applications, says David Wood, executive VP of research for London's Symbian, which developed the market-leading mobile-operating system of the same name. Having to pay for data is a real disincentive for consumers. And when they do download content or access data services over the cellular networks, they often suffer "bill shock" when they see how much it has cost them.

Existing carriers are going to have to start thinking on their feet if they don't want to get hurt by the disruptive effects of these Wi-Fi services, says Nuthall.

"We don't want to trash their business models," says Nigel Clifford, Symbian's CEO. But carriers will need to adapt and look at these developments in terms of what they are gaining, not what they are losing, he says.

Unfortunately, Wi-Fi coverage is currently not as widespread as the cellular networks, and many of the hotspots require users to pay for a subscription. Companies like Truphone are trying to increase their coverage by negotiating with subscription-based Wi-Fi providers so that their services will work in those areas as well.