Face unlock can enhance device security but should not be the sole measure for securing Bitcoin or other cryptocurrencies. The effectiveness of face unlock depends on the quality of the facial recognition technology, and even advanced systems can have vulnerabilities. Moreover, the overall security of the device, including a strong passcode or PIN, is crucial in preventing unauthorized access to cryptocurrency holdings.

For greater cryptocurrency security, you should try combining face unlock with additional protective measures such as strong passwords, two-factor authentication, and hardware wallets. The security of the cryptocurrency wallet itself is paramount, and a secure backup and recovery plan should always be in place. The choice of security measures should align with your risk tolerance and the value of the cryptocurrency you're safeguarding, with larger holdings warranting more robust security strategies. Relying solely on face unlock may leave your assets vulnerable to potential risks and threats.