This could be implemented in a computing device embedding in a fob or keychain that connects to a computer or smart phone via a physical connections or even blue tooth or similar. The application(s) requiring secure services can use a device with this design to implement arbitrary level of security as required by the application. The level of security achieved will depend more on the security processes that wrap the devices and software services than the device itself. It has a simple job, generate an asymetric key pair, exporting the public key and securing the private key. The security application may implement any processes it can design and implement to control the locking mechanism. Multi-factor authentication, linking to corporate or community based single sign on services, whatever is required for security can control whether the device is unlocked and willing to use its private key to make signatures for data presented.
If the device cannot be locked anyone with physical access to it can make signatures for identities associated with the public key. This is another way of pointing out that the security of the locking/unlocking mechanism is critical to system security. Any design should be reviewed completely, including all business and social processes that must be implemented and audited for any assurance of security and authenticity based on this technology.