Is it possible to recover an Arduino if it does not wake up after putting it to sleep I have an ATTiny85 controlling the power to a number of devices. When I first power on it will power the devices via a mosfet. Take the readings it needs to and then puts itself to sleep for 15 minutes then wake up and repeat.

My question is, because I am using the Watchdog timer to put it to sleep, I can't use the reset functionality of the watchdog (ie wdt_Reset). So is there anyway to detect a lock or hang if the ATTiny85 never wakes up for some reason or would I need additional hardware to check for this. If so what kind of circuit would I need.

Thanks
Not sure what you mean by "using the watchdog to put it to sleep". You can sleep with or without the watchdog enabled, and you can even use the watchdog to both wake you with an interrupt and also reset in case of a lockup. Check out section 8.5.2 in the datasheet...


  If WDE is set, WDIE is automatically cleared by hardware when a
  time-out occurs. This is useful for keeping the Watchdog Reset
  security while using the interrupt. After the WDIE bit is cleared, the
  next time-out will generate a reset. To avoid the Watchdog Reset, WDIE
  must be set after each interrupt.