Nokia has unveiled a cell phone charger kit for bikes aimed at developing countries with limited access to electricity. The kit costs about $20, starts working when you’re pedaling at 3 miles per hour and cuts off when you hit 30 mph. It matches the efficiency of a normal charger when you’re biking at 6 mph.

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Nokia says it sees potential for the charger in markets where bicycling is a central mode of transportation, like Amersterdam, the capital of the Netherlands and one of the most bicycle-friendly cities in the world — 40% of the city’s transport moves by bike.