I use Crashplan. It has a free option, which you can use to backup to an internal/external drive, or to another computer, either in your local network or not. When the backup destination is not available, the backup will not be executed. To be clear, I don't see how this would be different from the Windows Backup.
I have the family pack, pay $12 per month and can backup any computer that I control with unlimited storage. The only limit is upload speed. Then I have a local server at my home, which I use as second backup. I backup several family computers to this computer. Another plus: it works on Windows, Linux and OSX. The only catch: there is only one key to encrypts backups, so whoever has that plus the CP login, can open all backups.
You can backup to a friends computer for free, if he/she has CP as well. They can generated a code, give that to you, and vice versa. If you encrypt the backup, you cannot see the contents of the backup.