When monitoring client servers, I find it very valuable to keep track of of the currency of backups, particularly where there may be long periods between us getting hands on with equipment.
I can still feel the pain of clients who inadvertently disconnect their local backup solution, only to have a major crash weeks later.
In some of the small business deployments that we actively monitor, local Time Machine and CrashPlan backups are popular, and where appropriate, we like to get a notification if one of these has failed to complete a backup within the last day.
I have added the scripts we use to GitHub today, and hope you find them useful. They actively parse and analyse the completed backup timestamp logged by each service, so they are a little more reliable than checking file age on a specific directory or file within the backup.