Customizig window (and thus also dialog) titles can be done by requesting the window feature CUSTOM_TITLE, which must be done before setContentView.
So in your Dialog / Activity subclasses onCreate(), call the following:
super.onCreate(savedInstance);
requestWindowFeature(Window.FEATURE_CUSTOM_TITLE); // <- insert this
Then, after your setContentView, do this:
setContentView(R.layout.main);
getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.custom_title); // <- insert this
The layout can generally contain anything you want.
For a marquee text control. e.g. do this:
layout/custom_title.xml:
<FrameLayout android:id="@+id/FrameLayout01"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
>
<TextView android:id="@+id/caption_text"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:text="This is a very very long text that will not fit into a caption regularly, so it will be displayed using marquee..."
android:lines="1"
android:focusable="true"
android:focusableInTouchMode="true"
android:scrollHorizontally="true"
android:marqueeRepeatLimit="marquee_forever"
android:ellipsize="marquee"
></TextView>
</FrameLayout>
Due to some constraints with the marquee feature, the text view has to be made focusable and it will only be scrolling when focused (which it initially should be).