This was just released and is $10! Works great and works with RealVNC Enterprise, which allows you to have your entire session encrypted versus just encrypting your password upon connection, which is how almost all other VNC clients and servers work. I got it and set it up very quickly. I was surprised at how fast and responsive it is, even over 3G.
http://itunes.apple.com/us/app/vnc-viewer/id352019548?mt=8
http://itunes.apple.com/us/app/vnc-viewer/id352019548?mt=8