Android : Can I start an AsyncTask through a share activity, without displaying the activity?

The question is pretty much in the title. I want to know if I can start and execute an AsyncTask or something else in the background with the Intent data from the activity, without actually launching the activity. I looked for some information, but the only thing I found is how to register a service with your app, which isn't really what I was looking for. Bonus question: can I also display a notification or a small disappearing textbox on the display upon the AsyncTask completion/addition

Thanks a lot in advance