These old bikes look so victorian, haveing a bloddy liquid fuel run engine between ur legs is really stupid...i am waiting for these to arrive...
if not then i hope these kids come up with a better design
or there's a DIY option too:
this one's a super cool, super expensive option: http://pimobility.com/
but this is the one i like : http://www.ultramotor.com/in/product/a2b_metro