The Nike+ SportWatch GPS can only be linked to one NikePlus Profile at a time. The SportWatch is not configured for use by more than one runner.
You can transfer the SportWatch from one person to another user by linking it to a different NikePlus Profile. To do so, first complete a SportWatch factory reset in Nike+ Connect.
After resetting, you will be prompted to sign in to NikePlus when you upload your first workout. Enter the username and password of the NikePlus Profile you wish to link to the device.