We already have self destructing circuits[0], but it requires glass. Not something I'd think Apple would go with. Not to mention just dropping the device the wrong way won't just crack your screen anymore, but destroy your precious data. Not something I'd think the average user would want.

Or is there a different piece of tech that can self destruct when tampered with?

[0]: http://www.extremetech.com/extreme/214185-new-xerox-parc-pro...