Bootable cloud backup services?
My own solution to this problem, for both Macs here is 


Local Time Machine backups, hourly, on-site
Backblaze once a night [best for my data plan]


That way, even if the building burns down, my maximum data loss is one day.
Backblaze is accessible from any web browser &amp; files can be downloaded on demand; or if the data is huge, can be mailed on HD. It doesn't, however, contain the OS itself, only your data, prefs, settings etc.

Additionally, I swap out the Time Machine drives once a year, when I do any major upgrade - 10.10 to 10.11 etc.

I also make sure I have at least one clone of the current boot drive, though I don't keep it up to date on any regular basis. It will contain enough historical data - old installs I've lost the disks for, audio plugins where the authorisation site no longer exists, etc.  

I also make sure to have Recovery Partitions on more than one drive.

A further step would be to have an additional Time Machine drive, which normally lives off-site.

I just checked - Backblaze is also available for iOS &amp; Android - though it's not something I've ever really investigated.