Thread t = new Thread() {
        @Override
        public void run() {

            BufferedReader reader = null;
            try {
                reader = new BufferedReader(new FileReader(LOGFILE));
                String line;
                while (running) {
                    line = reader.readLine();
                    if (line == null) {
                        // wait until there is more lines in the file
                        Thread.sleep(POLL_MS);
                    } else {
                        // append to the log Label
                        synchronized (MyApplication.this) {
                            log.setValue(log.getValue() + line + "<br />");
                        }
                    }
                }
            } catch (IOException e) {
                // TODO: handle me
                e.printStackTrace();
            } catch (InterruptedException e) {
                // TODO: handle me
                e.printStackTrace();
            } finally {
                running = false;
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (IOException ignore) {
                    }
                }
            }

        }
    };
    t.start();

ProgressIndicator pi = new ProgressIndicator();
    pi.setPollingInterval(POLL_MS);
    pi.setIndeterminate(true);
    layout.addComponent(pi);