The mobile phone is the modern cigarette lighter for appreciative fans - but far more powerful.

It's one of the most dramatic moments of this or any U2 show. Suddenly, ninety minutes in, the lights are down and ten thousand people are holding their cell-phones aloft, turning the arena into a dazzling swamp of blue and white fireflies.

But this is not a moment that is just about rock'n'roll theatre. This is technological innovation being put to work for a profound cause.

When Bono invites people to take out their cell phones he is also inviting them to sign up to the ONE campaign and become part of a popular movement which will pressure Western politicians to end extreme poverty in Africa. This is how The Washington Post put it last week.

'Some way into each performance, Bono interrupts the music to deliver variations on this riff: The first time I heard about America, he says, it was because a man had landed on the moon. But now I want to talk about my generation's challenge -- not putting a man on the moon but bringing mankind back down to Earth by addressing extreme poverty. Take out your cell phones, the riff continues; make this place into a Christmas tree. And with that, the lights go out, leaving darkness punctuated by the fairy lights of 10,000 waving gadgets. "There's some light in the world," Bono's voice calls out, proving that rock stars can say ordinary things and yet somehow sound profound. "We are powerful when we work together as one." Rest of this article here.

The cell-phone moment in the Vertigo show is little short of breathtaking. It is, as the Chicago Tribune put it last week, 'like standing in a moonlit field, gazing at a velvet canvas of stars. About a quarter to a third of the 24,000 U2 fans raised their phones... then came the moment that separated the men from the boys, the girls from the women. Above the stage, the phrase, "Text your name to UNITE [86483]."

So if you haven't been to a U2 show this time around, if you've only heard about the cell-phone moment and are unsure how it works, this is what happens. As the opening bars of 'One' come through the PA, an invitation flashes up on the screens high over the stage for fans to text message their names to 86483 - the ONE campaign - and that information flies to a special aerial built by Sun Microsystems on the roof of the building.

The aerial then sends this information to the ONE campaign database ( it goes via 'an aggregation service in Singapore and then to a visualization server in California via a Web-service call using XML and Java APIs' - but perhaps this is too much information) and, as if by magic, some of the names of those who have signed up then return to the venue and are displayed on the screens for everyone to see.

Next day, those who texted get a response from Bono inviting them to learn more about the One Campaign to Make Poverty History. Already, more than 650,000 people have joined the movement. The goal is to collect the names of 1 million U.S. residents and persuade the federal government to dedicate 1% of the U.S. budget toward "basic needs--education, health, clean water, food, and care for orphans." According to ONE this "would transform the futures and hopes of an entire generation in the poorest countries."

If you want to know more about the complex and innovative technology behind the cell-phone moment in the U2 show, try this piece which claims that 'the resulting system not only represents the power and flexibility of a service-oriented architecture, but it also, I believe, reveals an early look at how text messaging will be used to build communities and to facilitate collaboration.' In other words you're not only campaigning to change history at a U2 show, you're a part of history being made even as you send your text.

Technology aside, here's the bottom line. This summer, President Bush and seven other leaders from the world's wealthiest nations will gather to discuss the fate of the one billion poorest people on the planet. In July the Group of Eight (G8) will discuss the social, political and economic conditions that contribute to extreme poverty. And as the political lobbying goes up a gear, on June ONE campaigners launch an unprecedented mobilization of Americans calling on President Bush to deliver a historic deal for the world's poor at the G8 Summit.

Whether or not you have managed to get to a U2 show this year, there is still time to have your own cell-phone moment - you can join the ONE movement here.

And if you want to know more about the G8 and this historic opportunity to fight global poverty check this link.