It is a RFID with a sensor and a powersource. By default it records a value saying its has not been tampered it. As soon as the sensor detects tampering, it will record a tamper value.
1. Active battery source: If wire is cut then record tampering.
2. Passive: Removing the tag will release a pin,
allowing a spring loaded mass to drive a mechanical power source. This can be either a Pizeo membrane, or a inductive coil. It is stored into a capacitor to power the processor long enough to record a tamper. (The coil could double as a RFID pickup)
3. Resistive: (Disposable rfid sticker) the RFID underside contains a painted resistive matrix. An ADC records the average voltage of multiple points in the matrix. When tampered, the sticker leaves a "VOID" residue that also take with it some of the resistive material. This changes the resistivity of the underside of the sticker, and thus the ADC readings. This will be picked up by the RFID reader on the next read. {Alternatively it could be a resistive mesh that is broken by a 'finger' if done as a 'loop tag' that is tugged too hard}
For the note: I think both of em is an obvious idea. And if it hasn't been made yet, its not because its too technical to do, but rather because nobody cared enough to make it.