As with drum heads, I'm guilty of waiting until the situation devolves into potentially problematic territory before biting the bullet and getting some new shoes. Shoes and drum heads also share in the fact that they are meant to be pounded and pounded and pounded until they invariably wear out. Waiting to change drum heads can lead to reduced sound quality, but waiting to replace running shoes can have a seriously negative effect on your runs and your body. As my dad has said, it's a lot cheaper to cough up for new shoes than it is to get new knees.
I try to be diligent enough about it, but this just leads to me doing some bad math and rationalizing putting off the change over. Which makes the shoe tracking awesome because it has fields to select the make and model of the shoes as well as at what mileage it will give a notification that it's time to re-up, from 200 to 600 miles depending on your preference. I was surprised to find the exact model of ASICS that I wear and there are tons of others to choose from in the scrolling menus. There's also an option to add in different pairs of shoes so that you can specify which pair you're using for each workout if you've got a rotation going.
For the most part, I like keeping my running gear simple. With so many activity tracking apps out there, it makes sense that new widgets are being introduced all the time to try and differentiate, but a lot of them don't interest me greatly. However, I can say with certainty that this particular function from Runkeeper will be of great value to me as it will help to keep me honest and cognizant of what's happening to my shoes and ultimately keeping my ankles, shins, knees, etc. in road-worthy condition.