From the Hackaday blog:
Physical access to electronics generally means all bets are off when it comes to information security. But in special cases this is just unacceptable and a better solution must be found. Consider the encryption keys used by point of sale machines. To protect them, the devices incorporate anti-tamper mechanisms that will wipe the keys from memory if the device is opened. One such technique is to use a mesh of traces on a circuit board that are monitored for any changes in resistance or capacitance. [Sebastian Götte] has been researching in this area and wrote a KiCad plugin to automatically generate tamper-detection mesh.