The latest version of Picasa includes an additional bit of software called Google+ Auto Backup, as reported by Google Operating System. The new software can be used to automatically backup photos and videos from user-selected directories to your Google+ account. Interestingly, the app has nothing to do with the Picasa service, even though it ships exclusively with the Picasa app.
The app can save unlimited 2048px photos to your account, or upload full-quality versions at the expense of Google Drive space. It can also intelligently copy media from storage cards and other devices that are attached to the system. Furthermore, the app can be configured to backup all media to a designated location on the local hard drive, putting all of your backed-up media in one convenient place.
You can get the Google+ Auto Backup app by downloading the latest version of Picasa.