Android

I have seen multiple solutions to let a Service / Activity communicate each other. However I can't understand in which context we should use them and why.
From what I've read around (android documentation and stackoverflow), these are the main approaches:

1. Bind to the service using bindService()
2. Use a messenger (it should be for IPC, but somebody uses it for same process communication)
3. Static instance (singleton) of the Service. This method could bring errors, what happens if the service dies? Null reference of that service. Shouldn't be better the first approach then this one?
4. Use LocalBroadcastManager and register the Activity for receiving. Basically, the Activity listen to the broadcasts sent by the Service. Viceversa, the Service in its onStartCommand dispatch intent actions sent from the Activity (explicit intent with custom action). For dispatching actions in the service, another solution could be intent filters on the service and implicit intents (android documentation says NO in the notes, even if I declare custom actions). How many chances are that someone else uses the same custom actions as mine?
5. Otto API

Now I'm really confused. Could somebody explain (if possible with examples) why and in which context we should use those approaches?
Are there other solutions other than the ones in this list?
Thank you.

Intent emailIntent = new Intent(Intent.ACTION_SEND);
emailIntent.putExtra(Intent.EXTRA_EMAIL, new String[]{to});
emailIntent.putExtra(Intent.EXTRA_SUBJECT, subject);
emailIntent.putExtra(Intent.EXTRA_TEXT, message);
emailIntent.setType("message/rfc822");

File publicFolder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
File inFile = new File(publicFolder, "snapshot.PNG");
if (inFile.exists() && inFile.canRead()) {

    Uri uri = Uri.fromFile(inFile);
    emailIntent.putExtra(Intent.EXTRA_STREAM, uri);

    try {                startActivityForResult(Intent.createChooser(emailIntent, "Choose an Email client :"), EMAIL_REQUEST);
        isSuccess = true;
    }
    catch (Exception e) {
        Toast.makeText(getApplicationContext(), "startActivity() exception thrown while sending email", Toast.LENGTH_SHORT).show();
   }
}