Ah, yes, the other side of the Halting Problem: not only can you not tell if your program will ever halt, but you also can't tell if your program has been externally halted.
Computers were doing that since forever though. Remember all those "your computer wasn't shutdown correctly, do try to do better next time would you" messages? Just write a bit into CMOS before doing a test, then assume the test failed if the bit is still set on next power up.
