Distress codes are an interesting idea. Although I'm sure that there are probably laws around supplying false information and/or destruction of evidence.
Dangerous, but what if your destruction code was 1 character out of 20 different to your actual password, do you reckon you could claim the intruder had fat fingers?
LE will generally create mirrored copies of your data before trying to access it and they'll decrypt it on another system that eliminates the risk of self destruction.
Interesting, because afaik Windows for instance, refuses to load if it's not run on the same hardware configuration it was installed on. Something to do with licensing keys and DRM and such.
I suppose they image it, use the password on the actual machine, and if something goes wrong or self-destructs, they'll always have the image (it just takes a little more time to convince Windows to load).