I don't think this will ever be useful. Where I am. Maybe other places it's already being done.
A friend was considering what kind of a business to put in a retail store location near where he lives.
Another friend and I have been thinking of possibilities as well.
One I came up with is about the dramatically rising price in electricity here.
But I did a rough estimate, and electricity would have to be bought at a price of more than $10 per kilowatt hour to pay just $1 per hour of biking.
Biking on generator bikes. Like a work out place exercise bicycles but with generators attached, and connected to a machine to show earnings, and to cash out. (Ticket take to other machine for actual cash, etc.)