I used the following hack to change the homeAsupIndicator programmatically.
int upId = Resources.getSystem().getIdentifier(\"up\", \"id\", \"android\");
if (
API 18 has new methods ActionBar.setHomeAsUpIndicator() - unfortunately these aren't supported in the support library at this moment
http://developer.android.com/reference/android/app/ActionBar.html#setHomeAsUpIndicator(android.graphics.drawable.Drawable)
edit: these are now supported by the support library http://developer.android.com/reference/android/support/v7/app/ActionBar.html#setHomeAsUpIndicator(android.graphics.drawable.Drawable)