You can add text to the screen and then make it visibile or hide it when a timer function is called.
Code:
#Add text to the screen.
text_2D = viz.addText('box', viz.SCREEN )
text_2D.setPosition(.5,.5)
text_2D.visible(viz.OFF)
def showBox():
text_2D.visible(viz.ON)
vizact.ontimer2(4,0,text_2D.visible, viz.OFF)
vizact.ontimer2(15,0,showBox)