They are in the market - just not ones that read emmision levels. Also the controllers and batteries are usually external.
With just a quick search on bike hub motors: http://www.evsolutions.net/9Continent.html http://www.goldenmotor.com/ http://www.falconev.com/E-Bikes.html
With just a quick search on bike hub motors:
http://www.evsolutions.net/9Continent.html
http://www.goldenmotor.com/
http://www.falconev.com/E-Bikes.html