One thing I've done as well is to set up a simple script which gets run from a cron job and will let me know via email if it hasn't seen any new photos uploaded

One thing I've done as well is to set up a simple script which gets run from a cron job and will let me know via email if it hasn't seen any new photos uploaded for 3 days (it's pretty unusual I'll go 3 days without taking a single photo on my phone). This provides a simple early warning for things like backup/sync apps getting killed by aggressive phone power management.