from click here
It is simple to set up and monitors all kinds of things.
Personally I don't use it to monitor costs, but use it to ensure my firewall and AV are running when I connect to the net.
I have also got it configured to start a very small programme, (that I made myself using VB), when disconnecting from the net. All this prog does is display a big bright yellow message on screen reminding me to check the BT 1571 service. It's appearance tells me that I am disconnected.
If you, or anyone else, would like this "1571" prog,(20kb) just email me using the envelope by my name.
Note that it is nothing clever, just a form that appears with a cancel button. I use "Tick" to start it.