You can pre-plan
According to the Garmin site it is NOT just an "In Situ" unit.
"Plan Your Adventures and Share Your Rides
zūmo 550 makes it easy to plan your next trip and share routes with your riding buddies. Plan trips on your computer before you start. Search for food and fuel stops and local attractions. Then, transfer your route to zūmo and go.
At the end of the day, share your favorite places and rides with other zūmo riders, and review your travels in Google™ Earth. SD card expansion makes it easy for storage and route sharing. Download routes to share with your riding buddies — even load mp3 files to your unit to enjoy tunes on the road. In addition, JPEG Picture Viewer lets you share photos of your adventures with friends and family."