|BTW, a better Watchdog might be good, like one that needs toggling within |defined time high and low *windows*. |So, also talking too much with the watchdog causes reset. |I believe Maxim or LTC make them. First of all, I think that rather than spending oodles of effort to make the PIC foolproof it's probably better to simply have hardware outside the PIC to prevent launch in unsafe conditions. The simplest way to do this would be to have a "deadman" switch for the launch current in series with the igniter: for the countdown to proceed the switch must be held pressed; if the switch isn't pressed the PIC is completely unable to launch the rocket no matter how it malfunctions. Since nobody should be pressing the switch any time the launch pad is not safe, nothing in the operation of the PIC should be able to pose any hazard. If the PIC malfunctions it may cause the rocket to launch sooner after the contact closure than it would otherwise, but if any sort of reasonable launchpad safety precautions are taken (e.g. don't push the button while someone's at the launchpad) that shouldn't be a problem.