Are there any rider aids for tyre management?

I have heard and seen how important tyre management can be. How do rider keep track of tyre life though? Is there an indicator of some type that shows how much tyre is left? Or is it completely based on feel?

I have heard and seen how important tyre management can be. How do rider keep track of tyre life though? Is there an indicator of some type that shows how much tyre is left? Or is it completely based on feel? http://ifttt.com/images/no_image_card.png