The Backblaze client does not have a way to only backup on certain hotspots:
However, what you can do is change the backup schedule to only backup during a certain time throughout the day. For instance, if you frequently tether to a mobile device during the day, you could set your backup schedule to only run at night.
1. Open the Backblaze settings either by using the Backblaze menu bar or task bar icon or the Backblaze application.
2. Choose the "Settings" button.
3. Choose the "Schedule" pane.
4. Select the backup schedule 'Once per day', and select the time period you would like.
If you do select a nighttime backup schedule, you will want to make sure to adjust your system sleep settings accordingly. You can make sleep and backups work well together in a few ways:
• Use system preferences to set a scheduled wake time prior to your Backblaze scheduled backup time (perhaps 11:50PM wake and a 12AM Backblaze scheduled backup time), and then resume sleep a few hours later. This would give a fairly large window for Backblaze to work on backing up, but wouldn't require user interaction to remember to wake/sleep the computer manually.
• Disable sleep, but still maintain the display sleep. This means the computer's display will shut off saving power, and not being bright late at night, but it would allow the computer to still be powered on enough for Backblaze to back up.