http://cgi.ebay.ca/500-W-Electric-Bicycle-Conversion-Kit-Hi-Speed-50k-h_W0QQitemZ220258676853QQihZ012QQcategoryZ158998QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
It doesn't use a hub motor, but uses a motor to drive the front crank and enables you to shift the rear deraileur for different gear ratios for climbing hills.
One drawback I can see with this is that whenever there is power supplied the motor, your chain is moving, whereas a hub motor, your chain is not moving. This could be deadly when you get your pants caught in the chain.
It doesn't use a hub motor, but uses a motor to drive the front crank and enables you to shift the rear deraileur for different gear ratios for climbing hills.
One drawback I can see with this is that whenever there is power supplied the motor, your chain is moving, whereas a hub motor, your chain is not moving. This could be deadly when you get your pants caught in the chain.