We have 3 NPM SLX installations in different parts of North America.
We have a 4th little NPM+SAM standalone instance that we use to monitor the other 3 NPM SLX instances.
Quite appropriately (IMHO) we call the little instance "watchdog" and it bypasses normal alerting paths and sends alerts to specific people directly.
Sort of like the movie Watchmen. Who watches the watchers ?
BTW: My background is electronics and thus the name watchdog. Look here http://en.wikipedia.org/wiki/Watchdog_timer