how to design a prepaid digital electric meter?

hi, i need to design a prepaid digital electrical meter, that will be able to send alerts when electricity goes off and when lower current is recieved, also there should be an ability to switch electricity off/on remotely. willing to pay for full support. want to use microcontrollers in this.

How do you want to do the prepay bit ? Unique Pin ? Smart card ? Mag card ? 
What range for your remote function   ? Method ? SMS ? Mains-borne carrier.