Currently there is a service tag.
It has 9,333 questions
It usually contains questions about
- android-service (3,881 with service and android)
- windows-service (870 with service and windows)
- web-services (388 with service and web)
I believe we should retag that questions with the more specific one, but with that large number of questions I believe it is not really doable by hand.
I believe that the other questions could be retagged en-masse: