Hi Snooz, I've been having a scout around for a device that would suit your needs, there are several on the market, this one looks pretty good. Its also not that expensive, particularly when you factor in what you will be saving, by knowing how much power your actually using :)
I have bought products of these guys before, and they are a very trustworthy seller. They are also in Australia, so their products meet all Australian standards for electrical appliances. I have seen monitors and meters that can be purchased outside of Australia, but these do not meet our electrical safety standards here, and you could run into trouble if you installed them.