After a disaster such as the recent Chinese earthquake, time is of the essence: aid agencies need to get to victims as quickly as possible. But that requires co-ordination on the ground, and if, as often happens, the local communications infrastructure has been damaged, the rescue operation can slow dramatically. Larry Gispert, president of the International Association of Emergency Managers, who has more than 30 years' experience in disaster relief, describes communications as the "number one problem".

"If you don't know where you are needed and you don't know where the resources are needed, it is very difficult to distribute them," he says.