If you do some searching, you can find some methods to hide WP that are essentially impractical. And I doubt any are totally undetectable. Use the methods that appeal to you in the Hardening link above. Use good internet hygiene, especially on the machine you access WP and your server from. Keep everything updated. Focus on security, not obscurity. Your site will be fine.
Most successful attacks result from weak passwords, outdated software, compromised computers (keyloggers etc.), or compromised LANs (packet sniffers etc.). All easily avoided if you keep your wits about you.