NAIROBI, Kenya (AP) -- Amina Harun, a 45-year-old farmer, used to traipse around for hours looking for a working pay phone on which to call the markets and find the best prices for her fruit.Then cell phones changed her life."We can easily link up with customers, brokers and the market," she says, sitting between two piles of watermelons at Wakulima Market in Kenya's capital.Harun is one of a rapidly swelling army of wired-up Africans -- an estimated 100 million of the continent's 906 million people. Another is Omar Abdulla Saidi, phoning in from his sailboat on the Zanzibar coast looking for the port that will give him the biggest profit on his freshly caught red snapper, tuna and shellfish.Then there are South Africans and Kenyans slinging cell phones round the necks of elephants to track them through bush and jungle. And there's Beatrice Enyonam, a cosmetics vendor in Togo, keeping in touch with her husband by cell phone when he's traveling in the West African interior.As cell-phone relay towers sprout on the slopes of Mount Kilimanjaro and the Serengeti plain, providers are racing to keep up with their exploding market.The numbers are staggering.Cell phones made up 74.6 percent of all African phone subscriptions last year, says the U.N.'s International Telecommunication Union. Cell phone subscriptions jumped 67 percent south of the Sahara in 2004, compared with 10 percent in cell-phone-saturated Western Europe, according to Mo Ibrahim, the Sudanese who chairs Celtel, a leading African provider.An industry that barely existed 10 years ago is now worth $25 billion, he says. Prepaid air minutes are the preferred means of usage and have created their own $2 billion-a-year industry of small-time vendors, the Celtel chief says. Air minutes have even become a form of currency, transactable from phone to phone by text message, he says.This is particularly useful in Africa, where transferring small amounts of money through banks is costly."We are developing unique ways to use the phone, which has not been done anywhere else," says South African Michael Joseph, chief executive officer of Safaricom, one of two service providers in Kenya. For an impoverished continent, low-cost phones make "a perfect fit."And cash-strapped governments which have had to give up their monopoly on land lines are looking to reap huge revenues from license fees, customs duties and taxes on calls."We all misread the market," Joseph said.The mistake, providers say, was to make plans based on GDP figures, which ignore the strong informal economy, and to assume that because land line use was low, little demand for phones existed.The real reason for weak demand was that land lines were expensive, subscribers had to wait for months to get hooked up, and the lines often went down because of poor maintenance, floods and theft of copper cables.Cell phones slice through all those obstacles and provide African solutions to African problems.Wildlife researchers in Kenya and South Africa have put no-frills cell phones in weatherproof cases on a collar that goes around an elephant's neck. The phone sends a message every hour, revealing the animal's whereabouts.It cuts the cost of tracking wildlife by up to 60 percent, said Professor Wouter van Hoven of the University of Pretoria's Center for Wildlife Management."You don't have to walk around the bush searching for the animals," he says. "I have sat around in Europe and was able to monitor animals in the mountains using a cell phone that had access to the Internet."Saidi, the Zanzibar fisherman, can now check beforehand whether prices justify him sailing his catch to the Tanzanian mainland, while Wilson Kuria Macharia, head of the traders' association at the Nairobi market, says he no longer has to spend two to four weeks at a time roaming across Kenya and Tanzania in search of fresh produce."A few mobile phone calls take care of what used to be the most grueling part of the business," said Macharia, 61.Cell phones also make traders more competitive, meaning better prices for farmers, he said.People who don't own a cell phone can use public telephone centers linked to cellular networks, creating badly needed jobs.Across the continent, in Nigeria, privately run cell phone services arrived in 2001 and started out charging $150 just to sign up. Nowadays four companies vie for customers by offering free sign-ups and introductory air minutes.The number of subscribers in the nation of more than 130 million has jumped from about 700,000 to over 10 million, and hawkers make a living selling air time cards to motorists trapped in traffic.On the downside, however, bus passengers on cross-country journeys have to turn off their cell phones because criminals are known to use them to coordinate highway robberies.Inevitably, cell phones have become status symbols. "If you do not have one, your friends will laugh at you and say that you are outmoded," says Akpene Rose, a 23-year-old hairdressing student in Togo, a tiny West African country where every sixth person is estimated to have a cell phone.And just as inevitably, there are those who wish they had never been invented.Ayi Aime, a 60-year-old Togolese, says both her school-age daughters have cell phones. "I do not know how they got them. I do not mind," she says. "But the persistent noisemaking, constant ringing, has become a nuisance."Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.