Just so you all know in the States Service Dogs do not have to wear any identifying ID or equipment, they do not have to be certified and no business can asked to see ID on the Service Dog. A business can only legally ask 3 questions. Is that a Service Dog? Are you Disabled? What Tasks does your service animal perform? Here some links that may help to answer some of your questions:

http://www.acesinfo.org/questions.htm
http://www.deltasociety.org/home.htm
http://www.iaadp.org/index.html

Nicole & Sheena