Desktop Lock is an iPhone application that will allow you to remotely lock your Mac or Windows desktops. It works in conjunction with a small application that runs on the desktop. For Mac users, the computer is locked using Fast User Switching, effectively suspending the current user. For Windows users, the computer is locked using the standard lock workstation function.

Requirements:


Mac

OSX 10.6 or greater with Fast User Switching enabled.
Desktop Lock Mac application (download from www.909apps.com/desktoplock)

Windows

Windows 2000, XP, Vista, 7
Bonjour for windows (Download link below)
.Net Framework 3.5
Desktop Lock application (download from www.909apps.com/desktoplock)
Once the desktop application is installed, open the desktop application and set a 4 digit numeric pin. You can install the desktop app on as many computers as you like. When you fire up the iPhone app, the configured desktops are automatically located and displayed in a table. Tap the arrow icon to set the PIN for each desktop. Now, from the main screen simply tap the desktop in the list, or tap the “Lock All Desktops” to lock each desktop automatically. To set up a desktop running on a fixed port, tap the '+' icon and add the host name or address and the port as well as the pin.

Bonjour for windows:
http://apple.com/support/downloads/bonjourforwindows.html

Server side installs for Mac and Windows can be found here:
http://www.909apps.com/desktoplock