Forget the concept of Windows services and Android services; in iOS, things are a bit different. You need to make few modifications if you want your application to perform a task while running in the background on iOS, since this functionality is not offered by default in Delphi for iOS.
A file named <appname>.info.plist is created when Delphi compiles your iOS application to the selected release type (Debug or Release). In <appname>.info.plist, <appname> is your application name and this file is deployed to iOS as info.plist. This is the file that iOS uses to determine whether your application uses background services.
Background services supported on iOS are described in detail in the Apple iOS documentation at http://embt.co/UIBackgroundModes.