I modified my Windows Phone 8.1 application (universal app with just the Windows Phone project live yet) to have a VoiceCommandDefinition (VCD) file in place and this works fine to start my app in foreground mode and handle parameters.
But I want to let my app quickly answer some app specific questions like it is described in this blog for Windows 10. I have tried to apply this blog but the app manifest modification fails. It does not know the:
uap:AppService
When I looked it up, it seems to be available for Windows 10 only. So I searched up the internet mainly MSDN and stack overflow, but I could only find examples that run the app in foreground.
Does anyone know an example how to provide answers to the Cortana content page with a background service?
Only App service can meet your requirements.
But App service is new in Windows 10, so you cannot use uap:appservice in Windows Phone 8.1 application. You can see App to app communication video from 26th minutes which introduce the app service.
So you can use universe windows app to develop. Sample is Cortana voice command sample as you see in that blog.