In xbmc the only services that can be setup to run when xbmc starts are python services, which are also addons.
These service addons differ from normal addons by adding the xbmc.service
extension point and specifying a python file to execute using the following line or similar in the addon.xml file.
<extension point="xbmc.service" library="default.py" start="[login|startup]">
Service addons do have an identical structure to current xbmc addons.
See the xbmc wiki page Automatically start addons using services, for further details.