A Hong Kong-based cycling goods manufacturer Tigra released BikeCharge Dynamo, a stylish and efficient pedal-powered dynamo system that can produce 3W/5.0V DC power to charge any USB powered devices.
It can fully charge most smartphones with 2-3 hours' ride. Having said that, it would be seldom that you will fully charge your smartphone with this product, but at least you can use GPS apps without concern for the battery consumption while riding a bike. Tigra also sells bike mount holders for smartphones.
Please watch the video on Youtube to see how it works.
It is easy to install and fits to most types of bicycles (The video installation guide is here).
The regular price is USD 111.99, but now you can buy it at a discounted price of USD 99. They ship from Hong Kong to worldwide.
It will make your bike life more comfortable and enjoyable.
Translation by Ryota Kasai