For nearly two decades Njoroge Kimani, a farmer in rural Kenya, irrigated his one-tenth-hectare plot the hard way: with a bucket in each hand. It was backbreaking work. The trip to a nearby well and home again left him exhausted, his arms and legs in pain. Last year Kimani, 62, saw his neighbor irrigating his crops with an odd contraption that looked like a stripped-down exercise machine. The man stood on two pedals and pumped them up and down. Two pistons connected to the pedals sucked water from a nearby creek and sent it through a network of pipes and out a spray nozzle.

Intrigued, Kimani borrowed the pump and tried it out on his own rows of tomatoes, maize and french beans. It worked so well that a year ago he spent $60 from his meager savings and bought his own, along with 36 meters of pipe. Since then he's expanded his plot to more than half a hectare and hired two employees to work the pump. Now he harvests during not just the rainy seasons but the dry seasons as well, and earns twice what he did during the best of the "bucket years." His wife even stopped nagging him about the money he spent to buy it. "Let's not talk about the 17 years I worked without this pump," he says. "If I look back, it was like having no job at all."

This most low tech of inventions is the latest brainchild of two innovation-minded social activists, Martin Fisher and Nick Moon. For the past seven years they've been marketing the blue-steel contraption, called the MoneyMaker, through agricultural-equipment shops around Kenya and Tanzania. Working through their nonprofit company, ApproTec, they aim not only to sell their product but to add to the ranks of the African middle class--through both the entrepreneurs who sell their pump and the farmers who use it. The pump is only the latest--and best--of a string of cheap and cheerful contraptions that they hope will help reshape the economies of these impoverished eastern African nations, just as the Internet and other high-tech innovations have reshaped the developed world. "We define technology in its true sense," says Fisher. "It's the application of science and engineering to produce tools, which in this case are being used to increase the productivity of farmers and help them make money."

ApproTec's products specifically target the problems of modern life in Africa. During the cold war, the United States and Soviet Union poured aid into friendly developing-country governments; health care, education and commodities like cooking oil were all free or heavily subsidized. When the Soviet Union collapsed, the prices of cooking oil and other goods increased threefold, and now Africans are short of cash for the bare necessities. Only 14 percent of workers in Kenya have a formal job, and half of them are employed by the government. Everyone else is living off the land and eating most of what they produce. The only asset most rural Africans have in abundance is their own time and effort.

The problem with Western technologies, of course, is that they're usually geared to saving time. The ApproTec founders, both veteran aid workers, realized that somebody needed to develop more appropriate tools. Fisher, a mechanical engineer who works full time on ApproTec, is a self-described technology wonk who doesn't believe countries can develop without productivity-boosting technology. After getting his Ph.D. at Stanford, he went to Kenya on a Fulbright scholarship in the mid-1980s. There he met Moon, a British carpenter who speaks fluent Kiswahili and had just sold his business renovating Victorian houses in London. Both worked for the U.K. development agency ActionAid, setting up groups of youth or women in businesses based on technologies like a roof-tile-making machine. When the aid group moved on, the businesses collapsed. The pair realized local entrepreneurs had to have a personal stake in making the technologies work. In 1991 they formed ApproTec.

The company's first product was a manual seed press, designed to give Africans an alternative to purchasing expensive cooking oil. Farmers put sunflower seeds in one end, cranked the handle, and cooking oil and a high-protein, high-fat compound suitable for animal feed came out the other. But Fisher says people in the administration of former Kenyan president Daniel arap Moi had a personal interest in the continued import of palm oil from India. The only sunflower seeds the government allowed into the country turned out to be hybrids that didn't grow well in Africa, making it difficult for farmers to produce oil.

ApproTec finally got some traction with its line of MoneyMaker pumps, including the $38 MoneyMaker Plus version in 2001. The pumps address a widespread predicament. The average Kenyan lives on a half-hectare farm with eight or 10 family members. As families grow in size and divide with each generation, their plots get smaller and must yield more food. The easiest way to increase productivity is to irrigate the soil year round, but only the wealthiest few can afford motorized pumps and the fuel to run them. For this reason, during the dry season crops like tomatoes are scarce and lucrative, but when it rains they're common and practically worthless. For farmers with an irrigation pump, "there's a huge amount of money to be made," says Fisher.

The challenge is getting those devices into the hands of farmers. Where other NGOs might give them away, ApproTec uses the marketplace. Moon compares the company's sales model to Coca-Cola's. ApproTec researches and develops its products, which include a manual hay baler and a block press, then has factories in Kenya and Tanzania make them. The company itself sticks to marketing--advertising in local newspapers and on FM radio. On a road leading out of Nairobi, a faded yellow sign says STOP! SEE IT HERE! IRRIGATE YOUR SHAMBA [vegetable garden]! An arrow points to a nearby nursery, whose owners are using the pump on its fields. At agricultural-supply shops like Blue-en-Spot in Muranga, Kenya, there are ongoing exhibitions of the technology. "People never buy a pump without a demonstration," says store manager Susan Wambui. "We just spray the water on the street. Everybody can see it."

ApproTec also keeps a database of customers and follows up with them regularly to measure their progress. About 30,000 farmers have bought the pump. Two out of three of the machines are still actively used. For every $1,000 ApproTec spends in marketing, Fisher says, it creates five new farm businesses that make more than $20,000 in new wages and profits--a return of 20 to one. He also estimates the devices generate $33 million per year in profits and wages--about 5 percent of Kenya's GDP.

Whereas philanthropists like Bill Gates pour billions into Africa for vaccines and AIDS treatment in the belief that a healthy population is a prerequisite for economic progress, Moon and Fisher think it's best to start out supplying tools that Africans can use to build their own businesses. Fisher confronted Gates on the issue at last year's World Economic Forum meeting in Davos, Switzerland. "Everything that changed America is at work here," says Fisher. Gates was dismissive, but Fisher isn't alone. "It's not a question of low tech, it's what you might call a people-level use of higher tech," says Maurice Strong, adviser to the secretary-general of the United Nations and a WEF fellow. James Ndungu Mburu, a farmer in East Africa, would agree. "If this pump was stolen, it would be like having my hand chopped off," he says. "Sometimes I dream about this pump, it has become that important to me." Let's hope the simple machines can fulfill more dreams, as well as populate them.