This is a pretty niche trick, but I recently figured out how to finally upload activities to Strava wirelessly using the latest Garmin Edge 510.
The newest Garmin Edge computers offer bluetooth sync to your phone, which is then used for real-time mapping of your rides, weather alerts, and when you're done with a ride, automatic uploads of data to the Garmin Connect site. It's very handy to just press "Save" at the end of your ride and have your data uploaded to their site but the only problem is the Garmin Connect site pales in comparison to the fitness site Strava, which offers more tools for analysis as well as a ton of social features. The problem with getting data to Strava is you have to sync your Edge bike computer with a USB cable after every ride, even though you can go a week or two without needing a charge.
Ever since I got the Edge 510, I've wondered how to easily transfer ride files from Garmin Connect to Strava so I could skip the cable-required-sync, and after a bunch of research I found a fairly odd little hack is available at GarminSync.com. The downside is that Strava doesn't currently offer an API, so you have to store your username/password at GarminSync, but once linked up, it does exactly what I wanted. You hit "Save" on your bike computer, it uploads to Garmin Connect, and a few minutes later that ride is also posted to your Strava account. It's great and does exactly what I wanted.
I suspect Garmin's running watches will soon share smartphone features as well, so this auto-upload-to-Strava thing may come in handy there too someday.