Announcement system downtime

Hello friend i like to have Announcement system downtime in my PBX system but just know i must write this module with AGI Programming so i need help how can develop this module…
explain about my module :
for example our system is down now and user with another telephone like cell phone call our office and register their number to our system then my technical group see this problem on the vtiger crm or like that…
please guide me if we have this module or not …so if we have this one please link to download else guide me hard :wink: thank you