I've just uploaded a new plugin called Watchdog, which monitors a user-created list of Indigo devices and sends a Pushover notification to your phone or laptop if a device has not updated for a specified timeout period. I used to monitor several devices with a combination of triggers, timers and action groups, but this solution is more elegant.
Only myself and my trusty beta tester have used the plugin so far, but everything seems to work well. If you'd like to try it out it's at:
https://www.indigodomo.com/library/407/