So i just picked up the Forerunner 610 (first GPS watch ever purchased) and signed up for the Garmin Connect. I like all the features but there should be so much more..
Garmin connect profiles: I have a username "robk732", and i can log all my runs and see all the stats of each activity. I can also share my activities on all the million social networking sites. I can see others runs in my area and download their data to my watch for "virtual runner" and i can look up others if i know their user ID. Garmin Connect should be set up more like this forum, when it comes to a user profile. Add information about yourself, add your friends that are on Garmin Connect and easily be able to see their activities (instead of bookmarking their username search). Basically Garmin fitness social networking (like facebook but aimed at fitness, sharing activities, locations, runs, etc.). This way i can see all my friends in one spot, see all their activities, maybe be notified when one of my favorites posted a new activity.
Activity Invites: Be able to send an invite to certain people with GPS location for a specific event, everybody can load this to their device and meet at that location for a group run. I would say 90% of my facebook friends could care less about a run I completed (that's why i haven't posted any).
Location Groups: So Mark, Steve & Amanda all go hiking at "Death Mountain Trail" but don't know each other. If I went to that spot and my device synced to the Garmin Connect, maybe notify me about the others who have recently been there (friend suggest).
Location Tracker: Foursquare gives people stats for visiting a certain taco shop frequently. Every time you go to "Death Mountain Trail" your profile will keep count. So and so has been here 13 times and this other spot 4 times and over here 8 times, etc. Then you can click on the number of trips and view the different runs/hikes/walks and see their fastest time, record to beat, etc. I think Nike's website does something like this.
You get the idea :)