Kenya is East Africa's largest economy. Its capital Nairobi is growing quickly. But so is the city's crime rate -- the Nairobi Metropolitan Crime Observatory says thieves steal an average of 10 cars each day.Kelvin Macharia has invented a tracking, or following, device that uses computers and wireless technology to help owners know where their cars are, and find them if they are stolen. Mr. Macharia is just 24 years old. He is the chief executive officer of Sunrise Tracking.He began working on his invention in 2012. Using $300 from his savings, he improved a system that was already being used to find stolen cars. His surveillance system uses a computer or mobile phone to tell owners where their car is. Mr. Macharia says if a car is stolen, the owners can find it using his tracking device. Owners are able to send a command to the vehicle through a text message. It immediately stops the car from moving. Experts say this shows the power of security solutions that involve mobile technology.Mr. Macharia used material available in Kenya to make his first tracker devices. When he was satisfied with the design, he outsourced the building of the device to a factory in China. He says his company is now worth more than $100,000 and has more than 100 companies as clients.Tony Wanga is one of those clients. He owns three minibus taxis. Car thieves in Nairobi have targeted these vehicles. Mr. Wanga bought trackers for each of his vehicles. The trackers cost $250 each. He says the tracker tells him where his vehicles are. He says when the tracker is placed in one of his vehicles, he can follow its travels as he sits in his office.Mr. Macharia continues to develop other security products. His other security products include car alarms and a camera hidden inside a pen. And he says he is building a wireless security camera that will be able to store video information for long periods of time.Mr. Macharia hopes his technological innovations give his clients the security and safety they want and need.And that's the VOA Learning English Technology Report. For more technology stories, go to our website 51voa.com. You can also watch vedios on the VOA Learning English YouTube channel.