I dislike that analogy. A "special grip" is analogous to a secret handshake or code, whereas fingerprints and retinal patterns are intrinsic and immutable body characteristics.
In fact, wouldn't an actual fingerprint scanner be more effective for this purpose? Having used biometric readers, I frankly would not trust my life to one. Nonetheless, it [fingerprint reader] would be infinitely preferable to any technique that required fine motor control in high adrenaline situations.
edit : this thread made me instantly think of Judge Dredd.
