Gtalk monitors your activity on your PC & if you are inactive for a long time, it sets your Gtalk status to "Idle".
Since almost everyone is familiar with Gtalk now, it's much likely that they will not disturb you, if your status shows "Idle".
Let’s say if you are busy with some important work & wish to communicate only with a few people from your gtalk list. You will probably want to change your Gtalk status to “Idle” so that others won’t disturb you. This is possible with a small utility called “galwaysidle”.
Galwaysidle: - Once installed will create 3 new options for the system tray gtalk icon.
1) Normal Idle: This will work the same way as you currently use it.
2) Always Idle: You can keep working & your gtalk status will be shown Idle to all
3) Never Idle: Your status will always show “Available” to everyone.