Is there a way, to build a local middleware service, without any interface?

Hi, I need to develop an app for IOS, that acts like a middleware, but only runs on one device and interacts with some of the apps on that device. I know with a URL I could make calls to another app and from them to my app, but I don't want my app to have an interface. So when another app calls mine, it should only process the data and the user shouldn't see anything. So I need some kind of background URL call. Is there a way to accomplish this? Thanks.