Did not know such things were made. On a side note, what voltage is output? It would be cool to run my GPS, charge my cell phone, MP3 player, and electric razor for those longer rides. I even found one on ebay from 1966, and I never knew it existed.
http://cgi.ebay.com/Sturmey-Archer-Dynohub-England-32-hole-Generator-Hub_W0QQitemZ300155872464QQihZ020QQcategoryZ420QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
http://cgi.ebay.com/Sturmey-Archer-Dynohub-England-32-hole-Generator-Hub_W0QQitemZ300155872464QQihZ020QQcategoryZ420QQssPageNameZWDVWQQrdZ1QQcmdZViewItem