More than 70 per cent of the world's population is expected to have a mobile phone subscription by 2011, according to the latest figures from Informa Telecoms and Media.

The research suggests that there will be four billion mobile subscriptions by the end of 2008 after rapid consumer demand in emerging markets such as China and India.

But this increase will then slow as the market reaches saturation, according to the firm's forecast, which predicts that only Africa will have less than half its population mobile by 2011.

However, Informa expects mobile operators to adapt to the slowdown of mobile subscription sales by targeting lower-income groups and increasing broadband internet and mobile connectivity.

"Mobile broadband services, and in particular the evolution of HSPA, have reinvented the business case for 3G technologies," said Informa analyst Nick Jotischky.

"As a result mobile internet services are helping to provide operators with new business streams, particularly within higher-income groups."

Meanwhile, web giant Google has asked computer scientist Alan Kay to speculate on the 'future of mobile'.

Kay predicted a number of innovations including Smart Alerts, which she believes will alert mobile users when something needs their attention. This is likely to work in a similar way to eBay's texts to consumers when they have been outbid.

"One very useful scenario is that your phone knows you are heading downtown for dinner, and alerts you of transit conditions or the best places to park," said Kay.

Phones will also start to replace sensor devices, Kay predicted. "Traffic reports can be based not on helicopters and road sensors, but on the density, speed and direction of the phones (and people) stuck in traffic jams," she suggested.