For what it's worth, I think Shoe Tracker could have all kinds of miscellaneous uses. Runkeeper does not have a generic tagging system, and Shoe Tracker gives you that capability, even if it is called "Shoes" :)
I'm using Shoe Tracker to track which cycling activites were done on which bike, for example, even if one doesn't care about the tires per se (I'm trying that right now but we'll see). There are no features needed to support this usage as things work fine for me.