In a previous post I explained how to install Newrelic server application monitoring for WordPress. I now realise that this is probably putting the cart before the horse in that one should install Newrelic Server monitoring first.
This is very easy. The instructions are here and at the bottom of the page it gives advice on how to use the monitoring tools.
AWS already has its own monitoring in place so potentially this is simply an additional load. However the are obvious benefits to having all your monitoring in one place.
I expect that this tools will be very useful for sizing servers because it shows “stolen” CPU. This is CPU that Amazon takes away from smaller instances when they exceed their paid usage. I think that the correct interpretation is that if there is a lot of stolen CPU you should up size the machine.