Dead Time is money, at least for the mobile phone networks. Increasingly skint, they've been looking for new places to make some cash and this time, they think they've found it: games, downloaded straight to your phone, played when you've nothing else to do.

Your Dead Time is soon to sacrificed on the altar of computer games played on the train. It's all because of Java, a programming language that, in theory, allows developers to write programs that will run on many different devices.

With the latest range of phones having colour screens and the ability to understand Java, the perfect partnership is created. On one side, mobile phone networks are looking for content, and on the other, the computer games industry is looking for a way out of the ever-increasing costs of developing big games for the console market.

Small teams, such as London's Morpheme, write two or three games a month. Even when selling them for only a fiver, the gamble is that enough people will have such phones to make it pay off. The simplicity of the devices is encouraging a return to the old school style of development. While console games take teams of 20 and multimillion pound bankrolls, Java games require only a couple of guys and a lot of caffeine. Steve Willcox - legendary developer for the ZX Spectrum, and the rest of the old school platforms from 20 years ago - is among those hearing the call: \"The risk-reward ratio is just too high with console games,\" he says.

His company, Elite Systems - having retained the licences to such classics as Bombjack and Paperboy - is busy \"porting\" its old titles to the new platform for both a new audience and the twenty-somethings who remember them the first time around.

They are not alone. Companies such as Namco and Capcom are converting their arcade classics to the new platform. The teenage players of such hit games as Street Fighter and Space Harrier have now, 10 years later, grown up to be the perfect target audience for these titles on mobile phones.

Other companies are looking at producing branded games that contain advertising for consumer products. Even now, there are more than 100 games available, free or for a few pounds. This isn't the first time the network operators have tried something other than voice-calls to make serious money - many will remember the massive failure that was Wap.

That died because the content was too expensive and not compelling enough to make anyone bother. This time, however, the networks believe the very latest phones - colour screens almost obligatory, for example - and the games themselves are enough of a draw for people to upgrade. That, and the way you download the games via the system called GPRS.

GPRS has been around for about 18 months for the common user, and sits on top of the ordinary GSM network. It differs from the regular GSM system in that you are charged not by the minute, but by the amount of data you pass over the network. You are no longer charged, in other words, for the time you spend waiting for a page or a game to download.

Many people, the networks especially, are betting large sums on the success of the game-playing phones. They are depending on the idea that these new capabilities will be the thing to \"drive phone-churn\" and \"increase revenue-per-user\" over the next few months. Christmas is seen as the big market.

The theory is that the key teenage and young adult market will get these phones for Christmas presents, and spend the new year downloading games and ringtones and sending each other picture messages. This will pave the way for mass adoption of 3G, whenever that might be ready for launch, and provide a welcome injection of revenue in the meantime.

Because these games are downloaded directly on to your phone, it allows for many interesting sales channels unavailable to, say, the PC gamer. For example, Telecom One last week launched a new TV channel on Sky. Called TX1, it features continual rolling previews of mobile games, along with instructions on how to buy them. By texting the short code shown on the screen to a certain number, you receive three messages, the last of which will be a bookmark that allows you to download the game.

All three messages are reverse-billed, which means you pay to receive them. In this way, you pay for the game. TX1 is expecting to price the games at around UKP4.50 each, and has more than 40 in stock. Many of them are fully licensed versions of old arcade classics, made possible because today's phones contain considerable processing power.

Interestingly, the feeling among Nokia executives is that this amount of power goes some way to making 3G irrelevant: \"Gamers have spent the past few years working out how to run complicated multi-player games over 56k modem connections over the PC: we have that with GPRS now, so why do we need all that 3G bandwidth?\" said one.

Despite their pro-Java bluster, however, the phone manufacturers aren't helping anyone. While they may be proud of their current range - phones such as the Nokia 7650 are amazing bits of engineering - people are already beginning to notice their limitations, especially when contrasted with their ideas about precisely what they want to do with these devices.

For a start, the developers tell me, the way Java has been installed means the programmer cannot access any of the bits of the phone that actually make it interesting. From a Java program it is impossible to access the camera, the address book, or - in phones that have it - Bluetooth.

Nor can an application send SMSs, or talk to any built-in GPS system. In many phones, you can't even get the phone online from a Java application. The promise of interesting location-based games and applications is pretty much shot through, unless the developer writes the application in another language and targets it at one particular phone.

The whole point of using Java, with its write-once, run-on-any-device ideals, is somewhat lost when you talk of anything more ambitious than a really simple game. Even for the simple stuff, development is made harder than it should be: although every phone has a different screen size, button configuration and sound capabilities, there is no direct way for a program to find out what device it is sitting on.

Developers are forced to figure out hacks (by trying to write to a part of memory they know only exists on a certain phone, for example, and waiting for the error message) so that programs can run at all. The problems do not stop there. While the phone networks are hoping for a bumper Christmas, their pricing may let them down. Given the cost of the phones, only one is available as a teen favourite pay-as-you-go handset: the Vodafone Live Sharp GX10 at UKP349.99. The price is equivalent to a Nintendo GameCube and five games, or a DVD and TV combo.

Neither is pay-as-you-go GPRS cheap. According to Vodafone, the average game will cost more than a pound just to download on the pay-as-you-go tariff, on top of the game's cost. Competing in the Christmas market is not going to be easy. It gets worse. According to industry sources, at least one of the UK mobile networks has no way to check if pre-paid mobile phones have enough credit to allow the user to purchase the game.

Premium rate SMSs, like those sent by TX1, are sent first, and billed later, meaning it is possible for an unscrupulous user to buy the game with an empty pre-pay card - thus paying nothing - and then download it on to their phone via a new GPRS account. Neither can networks currently, at least, provide itemised billing for things bought via premium SMS.