As a starter for 10, i'd suggest you look at the SysLog options available to you under SystemMaintenance menu. On my 2820 you can elect to receive either mail or 'syslog' notifications. The mail option might not throw an exception when you switch to the alternative route; if it doesn't, then probably time for you to 'wiki' for 'syslog' and read up about what programs you could use to 'listen' to the syslog events that your router could send to it. Once your third party program is receiving events, do a test to simulated the scenario and see what notifications you receive ... it is up to you how you choose to handle THE event for the situation you want to handle, eg you could set off your sprinkler system, send a text to a pager, launch a weapon, or send yourself an email etc.
My instinct tells me that you are likely to find a solution via the above 'Syslog' method, via either its 'WAN log' or 'DSL/Router Infocmation' log options. NB if you dont intend using Syslog after playing, i'd strongly advise you to turn it off, as some Syslogs will bring a system to a halt if they go 'unread'.
