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Here's an interesting video from Nicaragua: a pedal-powered phonebooth. 

While an "interesting" project for educational value, I'd say as far as a business idea, here is one that will never work.

As I wrote in http://central-america-forum.com/shared-images/bicycle-generator I had also made a bicycle generator (but mine was just to charge a battery for general use (lights/tv/computer/tools/blender, etc).

In addition to the problems of riding a stationary bike in a hot climate, even more problematic is the expertise required to build and maintain something like this.  You practically have to be an engineering college honors student to pull it off.  And how many engineering college honors students are going to invest $1000 in order to sweat all day long and earn $10 per day?

Not too many.

I don't want people to be discouraged from trying crazy things, but just remember: a hobby is a hobby, and a business is a business, and wishful thinking alone can't change one into the other.