Exactly. Individual peak power is far different from realistic continuous power. And even that will vary greatly from person to person.
Some people can do a solid 100+ watts and hour for extended periods without any difficulty. Others couldn't do 20 Watts for more than a few minutes without exhausting themselves.
Usually its the ones who couldn't do the higher exertion work that claim they can easily do it but never show them selves actually doing it. Then there are others that do that level of exertion all day every day for years and never think twice about it.
Here is how I see it from a single application in my life.
The power pack for my laptop is rated at 19 volts 4.74 amps and when I am using it while the battery is in a high charge cycle it draws around 80 watts and stays at that draw for more than an hour.
To reproduce that equivalent output from a human power source a person would need to generate over 100 watts of physical output to get the roughly 80 watts of electrical energy needed for the laptop to work and charge at the same hour plus time frame.
Thats well beyond the realistic continuous hand cranking capacity of most everyone.
If its broken down into a easier but still reasonable effort of 20 watts per hour thats still some 5 hours of non stop cranking just to charge up a laptop and use it to any degree.
I still dont think many people would actually ever put forth that amount of effort for that time frame just to use their computer for a hour or two. I sure wouldn't.
Even if a exercise bike type of generator system was used I would like to see anyone pedal a 100 watt exertion level for an hour or more while working normally on their computer at the same time!
The OPs design would have limited applications for very low power usage applications being done by people with far more time than money. But those people usually cant afford the Ipod, cell phones, and other lower power electronic toys that are within the realistic human powered recharging range.
And I seriously doubt they could afford the charger device in the first place.
For anyone who says thats why you give them out charitably to the low income people, well someone is still paying for them at some point anyway and if its me thats expected to pay for one I would rather let a few dozen bums stand around in my shop all day with a hundred power pack chargers plugged into every outlet and power cord they can find for free first!