Interesting problem... I don't have experience with these products, but have been tinkering with Schmidt hub dynamos and run some experiments to see how much power can be extracted at different speeds.

One basic limitation of hub dynamos is that even in the best circumstances, only 6 or 7 watts can be extracted when traveling 20mph. Lower speeds will produce less power. If you are trying to charge an Apple product that expects to be able to pull 2 amps from a 5V source, the dynamo will never be able to do it.

If you want to charge a battery pack, then that's more reasonable. You'll still need to estimate how much power and energy your devices will require and how much the dynamo will be capable of delivering.

Your best option might be to find a dealer that is willing to let you try out some of the devices that you are considering. ... but if you get lucky and one of the bike forums members knows the answers to your questions, I'm interested in hearing what their experiences have been.

good luck,
Steve in Peoria