I believe there is one system around, being trialled...(might be in Victoria?) where you can send a message direct from your pager, to confirm your attendance...
Basically, the pager message for the call comes through, if you can respond within the appropriate time frame, you press the relevant button on the pager, and your message is sent to the releveant person / perole / computer advising of how many are coming....
However, having said that, I have a fairly good idea of who is around the district on any given day, and how many are likely to respond.
Particularly on bad fire days, I know exactly who is around, and who can respond, and when......
But my brigade is fairly small, and not a huge number of calls, so it is fairly easy to know the availability of the crews...
Pip