I would also like to track the distance for shoes. But a more general feature might be to define equiment categories by the user. E.g "shoe", "bike" or "horse". Of course it must be possible to assign different items per category.
It would be nice to be able to track mileage for multiple shoes. Have the phone allow you to pick which shoe you are wearing and then track the miles on it.
Also, a graph of the HR on the gps-sport site would be useful specially if it could be tied to or coordinated with the street map.