Wireless devices are often used in application scenarios with strict security requirements. Examples are physical intru- sion detection systems commonly used to protect factories, airports or government buildings. In such scenarios, addi- tional security features such as tamper detection are highly desirable to complement traditional cryptographic mecha- nisms. In this paper we use channel state information (CSI), extracted from off-the-shelf 802.11n Wi-Fi cards, to calcu- late a tamper-evidence value for transmitters. This value enables detection of tampering due to device movement or replacement. We describe algorithms for tamper-evidence value computation, discuss the interpretation of this value and evaluate its effectiveness.