No that won't work, you have to assume your outputs will lock up high or low. You need a pulse detector.
You wanna get crazy eh? Ok here you go... 10 SECOND WATCHDOG by BDub
Pulse D2 at the prescribed rate to keep RST high. ~10 seconds after pulses stop, RST pulses low for 250ms. RST will continue to pulse low every 10 seconds if pulses do not return. Input is AC coupled, so pulses can stop high or low without a problem. R7 can be omitted as there is a 10k pull up on the Spark Core.
If you are looking for something to do, go ahead and build it! If you just want to get it done easily, kindly ask @Sparky for his ATTiny85 code 