Design a Status Page & Alert system for SQL/PHP real time database (Energy Monitor )

We have a ‘Smart Metering’ devices installed in a number of sites. Each site reports to our MySQL db once per minute with a number of values. (power consumption/circuit, voltage, frequency, etc. )
The current db is MySQL & the viewing site is PHP
To view example site go to :-
www.knowatts.co.uk
User : Polymeter16
Password : example

We need an overall view of the status of all of our sites. There could be 300-3000 in next 6 months.
We need to know if they are all reporting correctly, or if not how long since they last reported & what faults they might have.
we need to be able to acknowledge alarms and manage the view.

We hope you will have some suggestions.

Simon

Attached is a brief of the job and the data sheet on one of our products.