I would like to write an application that would run on the Android device as a service and then with other application(s) I would access to this service with calls. Is there a way to expose public API from an application/service on the Android device? And how to access this API from another application?
Thanks for help
Look into Intents, AIDL (binder) and content providers.
Intents are smal "simple" asyncronius messages, AIDL if for a more RPC type of API, usefull for a more complex/more data API. Content providers are a way to expose data from your App, like a contact list or something.