M+ D is very customisable so it probably would be possible but it doesn't seem to have the option "out of the box"  Immediate choices are: 1. An Enhancement Request logged for M+D (as I'm sure others would benefit from this)  or  2. Request the Foglight professional services team to spend time generating that alert (Contact your account manager to set this up)   
We would like to receive an email if a computer group (specifically a cloud) in vWorkspace has few or no available (logged off) machines.  We have vWorkspace Monitoring/Diagnostics (Foglight) installed and sending emails, but have no idea what rule to set or build to do this. We have vWorkspace 8.6 (not .1) and vMD 5.7.1
How to alert when computer group has no available computers