To make a listing there could be an "Upload Track Data" to a secondary site as part of the Waymark itself.
Neat idea, although I would assume that you'd have to register on the external site, and although I'm not sure there are specific restrictions on Waymarking of such arrangements, like there is on Geocaching. If it did get the green light from Groundspeak to use an external site to enhance the Category, I'd recommend
Everytrail. It also has the advantage of geotagging photos, and a pretty slick iPhone app. Here's a tracklog from my hike yesterday in Pebble Beach:
Del Monte Forest