Atmel ATTINY13 estop controller

So I have what I hope to be a very simple project. I have a PCB with an attiny13 microcontroller and I need it to do the following. Upon start-up the board needs to wait for 3 seconds then check for a heartbeat that happens every 750ms on a specific pin. Once it has found the pulse then it will pull an gpio pin high. If at any time the pulse is not found within a time limit then the gpio pin is brought low and another pin is brought high to sound an alarm. If the pulse returns the board will return to normal operation. Ideally the heartbeat timing should be averaged over a few readings to prevent false alarms. Also a time window should be used, for example it would accept between 700 and 800ms pulse times but if the pulse was missing for 3 beats then it would sound the alarm. The 3 second startup delay needs to be configurable The 750ms pulse time window needs to be configurable The time delay that it waits before it triggers needs to be configurable The amount of time the board remains in alarm mode before reactivating needs to be configurable This needs to be compiled with winavr, a makefile supplied for programming with a usbtiny PB0 is where the heartbeart signal will be coming in PB3 is the Alarm output which will be brought high to sound the alarm PB4 is the output that will be enabled once a valid heartbeat is found