Of several 3CX's is a different story in this case. It is common to have 1 administrator who would want to monitor multiple remote 3CX installations.
This is a good idea - in fact this is something we are planning to provide especially for remote office installations. There is no exact timeline for this feature but we definitely see the benefits of having this feature - The monitoring will also include monitoring of trunk status, bridge, tunnel status, remote offices, performance counters, extensions etc. Point taken.