My key objection is that it doesn't offer any additional value: if you are the sort of customer who would do this, you are also the sort of customer who would implement the same chain of commands to backup to a virtual machine that you owned, eliminating the attractiveness of baxx.dev as a aggregated target. What additional value can you add?
* i have actually implemented this kinds of systems multiple times and always failed at the 'who watches the watchers' and usually had broken backups (as in i usually needed them few years after the system is written and by then something is always wrong)
* in the future it will use contextual bandits to probe for broken backups (such as: hey, is file XYZ with size X uploaded at Y weird?) and learn from all the customers triggering the AI flywheel, more backups more data, better contextual bandits, better service, more customers (the idea is to use bandits[or something else with exploration factor] for probability of "good" notification)
so in few words: value = out of the box alerting + nice api + machine learning (not implemented yet) + good price (no cloud)