One way to think about your fear is, shouldn't that just be a tarsnap feature?
Add some metadata for a machine that tarsnap should expect a once a day/week/month backup from this machine, and if it doesn't get one, to send you an email?
Add some metadata for a machine that tarsnap should expect a once a day/week/month backup from this machine, and if it doesn't get one, to send you an email?
Until the day when Colin considers it in-scope for Tarsnap, I recommend Deadman's Snitch for this purpose. I literally spend more on DMS to monitor Tarsnap than I spend on Tarsnap. No, I don't think that is just, either.
And the discussion on HN https://news.ycombinator.com/item?id=7523953
(This may be slightly overbuilt, but I felt it justified to get peace of mind, given AR's fair degree of importance to customers/myself and the enterprise-y customer base. In particular, I would not have been happy with any monitoring solution which would fail if I lost network connectivity at the data center.)
$15 a month is far below my care floor for making sure that my backups are working and that I do not get sued into bits.