Thanks mharvey& Jfrazier I'll look into these as possibles. What are your thoughts given that we have multiple ESX hosts all sending in heartbeats, as I'd need to differentiate between distinct devices (for obvious reasons) so that the one that hasn't sent a heartbeat is picked up ?
I guess if each devices traps wrote to a file then the file age monitor would be a way forward although each time a new ESX is placed in use, I'd need to create additional monitors (which, albeit small numbers, eats into the SAM licences...) I think at time of writing we have around 30 ESX hosts in deployment (with more coming).
I suppose my ideal solution would be something like the same way NPM polls devices (but sort of in reverse) whereby if a device hasn't notified the Orion server it's "alive" to then have an alert notification sent off the back of that.
Great discussion btw, please keep the ideas/suggestions coming