It's not just people who have mobile phones now - machines are getting them too and they've started talking to each other, but hopefully with the aim of making life better for us, rather than taking over the world.

Called M2M, for machine-to-machine communications, the idea is to make use of the existing GSM infrastructure, thereby avoiding the need to hunt for Wi-Fi coverage or run cables out to remote sites. The idea has been around for a while, but has become much more practicable of late, says Steve Whitehead, technical director at M2M consultant Comtech.

"M2M is not new, but it was largely local and proprietary," he says. In addition, in the past such projects involved many partners, so end-to-end systems could be hard to build and difficult to understand. In addition, many industries were - and are - slow to adopt new technology.

"What's changed is the advent of standards such as XML and of IP connectivity via GPRS," Whitehead says. "Now that we can wrap it all into a simple solution on robust proven technology, it's become a standard product and we can get customers to market in two or three months."

The necessary GSM data modules - basically a mobile phone in a black box, with a serial interface and a power socket - are also less expensive than they were, adds Melissa Jenkins, Orange's telemetry product manager.

"The module price has fallen significantly, a few years ago it was several hundred pounds, now it's £100 to £150," she says. "We've been talking about monitoring vending machines for so long that it's about time it happened."

Other applications might include prioritising a technician's site visits, say, or monitoring the usage of consumables and equipment. M2M is being built into photocopiers, so replacement toner or a service call can be sent before the customer even notices that there is a problem.

In a lot of cases, the same job could perhaps be done without the need for wireless fees by using a phone line or Internet connection, but that introduces others costs and dependencies - plus of course it needs a data cable.

One of Comtech's customers for M2M is the UK lottery operator Camelot, which is trialling a wireless advertising display. Camelot currently sends out weekly sales packs to retailers, and then relies on the retailer keeping the point-of-sale display up to date with the latest jackpot figures and with information on new games.

The M2M alternative has rolling LED displays which can be programmed with messages over the air. All the shopkeeper has to do it plug it into the mains and put it in the window.

Another application is door-locking, where BearBox uses it to control PIN-coded locks on remote offices or unattended delivery boxes. You use a Web browser to control who has access to which doors, the settings are downloaded to the lock via GPRS and it also reports back on who has used it - each user has their own PIN.

BearBox CEO John Hale says that the aim is to replace PINs with proximity smartcards, at which point it could become an option for homes as well as business premises. The company sells the locks at £350 each plus a £10 per month service fee, you then add your own SIM and airtime contract - M2M tariffs are typically £4 or £5 a month, plus £1 per MB of data.

The only requirement for all these devices is power: "You can use solar, but it's easier and more reliable to use mains," advises Hale.

Orange has been offering wireless metering and vehicle tracking systems for some time. For example, its FleetLink service locates lorries in real-time, feeding back location on arrival and departure time and route history, both to allow better fleet management and to track compliance with rules on drivers' working hours.

Melissa Jenkins says bus operators are using M2M as well: "For example, Metroline did one simple thing - it figured out how far apart its buses are. The bus driver can then get a message, asking him or her to slow down or speed up to improve the spacing. It makes a huge difference to the user experience, but there are other, compound, justifications too, for example you need fewer buses to run a good service."

This is a common feature of M2M deployments, she adds. "Our customers do it for one reason, and then find others to back the decision up. Having implemented it, they find new things they can do."

She acknowledges that each individual M2M device makes relatively little money for the network, with an average revenue per user of £5 a month. The key is volume, she says - there are so many machines to connect, and the cost of connecting them is so low, that there is still good revenue to be made.

Plus, M2M users are 'sticky', meaning they are less likely to change networks every year, so the revenue is more reliable - Jenkins won't give figures but hints that it is already 10% to 15% of Orange UK's revenue.

"It's not like handsets, where we sell thousands a month. With telemetry we sell hundreds or thousands but it's over three to five years," she says. "Yes, it costs to set up a connection, but we are automating that."

She adds that it did require a change in mentality, as well as reconfiguring the network to cope with low-use, stationary devices: "There were unexpected problems, like you don't use a SIM for ages and it falls off the systems."

There are other issues too, of course. One is that all GPRS devices have dynamic IPs, so you can't use the IP as a way to interrogate the device. Orange's solution is to use the phone number instead; this works, but it does mean that software must go through Orange's systems.

SonyEricsson's M2M business manager Gopi Krishnamurthy adds that GPRS is only one part of the M2M puzzle - SonyEricsson sees the need to bring in other wireless technology such as 802.11, Bluetooth and Zigbee, as well as telemetry protocols such as M-Bus, DLMS/COSEM and SCADA. He points to applications in Sweden such as remote radiation monitoring, and telemetry on heat pumps and industrial machinery.

"Hardware prices are falling 16 percent a year," he adds. "If the cost of the meter is £20 to £25, you can't have a module costing four times that."

"It's a very different world from a few years ago," he says. "We have solutions that work, so now it's how can I transform my business? How will this extra information change the way I work?"

On a similar tack, Melissa Jenkins has a few key tips for anyone considering M2M. "Telemetry changes businesses - it's the same kind of fundamental change as BPR [business process reengineering]," she says.

"Look for three to nine months ROI - a year makes it hard to justify. Plus, all our customers pilot before they buy. Lastly, it's important to start simple and not do too much, because it breaks your business case."