So the Promise Pegasus thunderbolt external storage array is a super piece of hardware for the price. One thing they list as a feature is the ability to email a user in case of a drive failure. One problem, though, is that I could not get this to work for me.
A nice feature of the system, though, is that the included Promise Utility GUI that ships with the array also installs quite a full featured command line utility. For instance, you can get a quick report of the drives in the array by issuing the following:
w00t!
I wrote a quick little Ruby script to grab the drive information and send me an email in case the status is not "OK".
DISCLAMIER: This snippet is provided as-is. I am not guaranteeing this works at all, and is using the assumption that the status will change from "OK" to something else if there is an issue with a drive. Use at your own risk.