Register a broadcast receiver for known action intents and handle the broadcast to show or do something with the track information, source:
public class CurrentMusicTrackInfoActivity extends Activity {
    public static final String SERVICECMD = "com.android.music.musicservicecommand";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        IntentFilter iF = new IntentFilter();
        iF.addAction("com.android.music.metachanged");
        iF.addAction("com.android.music.playstatechanged");
        iF.addAction("com.android.music.playbackcomplete");
        iF.addAction("com.android.music.queuechanged");
        iF.addAction("com.htc.music.metachanged");
        iF.addAction("fm.last.android.metachanged");
        iF.addAction("com.sec.android.app.music.metachanged");
        iF.addAction("com.nullsoft.winamp.metachanged");
        iF.addAction("com.amazon.mp3.metachanged");     
        iF.addAction("com.miui.player.metachanged");        
        iF.addAction("com.real.IMP.metachanged");
        iF.addAction("com.sonyericsson.music.metachanged");
        iF.addAction("com.rdio.android.metachanged");
        iF.addAction("com.samsung.sec.android.MusicPlayer.metachanged");
        iF.addAction("com.andrew.apollo.metachanged");
        registerReceiver(mReceiver, iF);
    }
    private BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            String cmd = intent.getStringExtra("command");
            Log.v("tag ", action + " / " + cmd);
            String artist = intent.getStringExtra("artist");
            String album = intent.getStringExtra("album");
            String track = intent.getStringExtra("track");
            Log.v("tag", artist + ":" + album + ":" + track);
            Toast.makeText(CurrentMusicTrackInfoActivity.this, track, Toast.LENGTH_SHORT).show();
        }
    };
}