I've tried the accelerometer trick and found that it was difficult to set thresholds such that careful attack would be prevented while seismic upsets wouldn't make the device unreliable (or at least where it was easy to be confident that seismic upsets wouldn't trigger it).
If it fails often that itself becomes an attack vector. "Oh? it failed again... happens once a month when they move the piano next door. just reset it"
Right, it's not that acceleration exceeded some small threshold, but either it has exceeded a large threshold or that an integral of acceleration over the last N seconds indicates motion of more than a few centimeters. But you really want to integrate all sensors.
If it fails often that itself becomes an attack vector. "Oh? it failed again... happens once a month when they move the piano next door. just reset it"