New Relic is one of those things you keep seeing while browsing the net for nerd stuff.
Basically, it's a 'plugin' for your website that will monitor any kind of information you can think about: application speed, code errors, cpu and memory usage and a huge amount of data that will satisfy everybody.
It's data porn!
As a nice plus, just for trying the service you'll get a free t-shirt! Yes, simple things make me happy.