Harvesting Eddy currents - but how??

[gotwind2]

Hello all.
I read an article on the great Treehugger website this morning, and it has bemused me all day 
It appears a German engineer has found a way of harvesting the eddy currents induced by a strong magnet in close proximity to either a steel or alluminium rim of a bicycle wheel - the outcome a small power supply to illuminate some high performance 'Cree' LED's for lighting.

I've always considered eddy currents as a negative thing? - it seems not, or maybe it is B/S 
http://www.treehugger.com/gadgets/help-kickstart-first-compact-contactless-bicycle-dynamo.html

There is a direct website link to the product page here http://www.magniclight.com

Can anyone help me understand this?

Thanks.
Ben.

[dinges]

Can anyone help me understand this?

There was a discussion about it on this forum yesterday:

http://www.fieldlines.com/index.php/topic,146522.0.html

[gotwind2]

Thanks Dinges,
I like your explaination best, well observed/written - It appears to be nothing that ground breaking technically.