Read AVR watchdog timer
Set the watchdog to 1s second, then set it in interrupt mode, when the interrupt happens the watchdog set itself again to Reset mode and then your code has to manually set it to interrupt mode, that way you can use the watchdog timer as a 1 second timer and the still have the watchdog functionally because if after the interrupt execution there is a one second window to set the watchdog to interrupt mode before the timer expires and reset the micro. 
I have use the watchdog this way in an attiny10