I'm interested in ways to protect my application from the effects of EMI,
power supply spikes, lightning, et. I am considering some of the following:

Using the WDT to generate resets; re-initializing registers, to prevent the
PIC from hanging in a loop in the event the PC is corrupted.

Spreading SLEEP instructions between called routines, and testing for
invalid resets or WDT timeouts to call a error handler or re-initialization
routine.

Loading a register with a unique number, according to the routine that the
code is executing, and testing for this number in other routines that rely
on the calling routines data.

Periodicaly generating and testing checksums in register and User EE Rom.

Any other idea's or comments? References to good books or application notes
from any manufacturer's?

Has anyone experienced problems that would justify going to this much trouble?
Thanks.