I've decided to go ahead and release my own version as an alternative.
The program can (and probably should!) be mapped to a hardware button using the Buttons control panel applet. I run mine on Button 4(hold) because I never use the voice recorder. This also prevents locking the device unintentionally.
I have also added two minor features to the application that some might find useful. You can optionally put the device to sleep after it is locked (same as pressing the power button) and you can configure a program to run just before the device is locked. This is useful if you have an application that you may want to look at frequently without unlocking the device. (Contacts, Calendar, a full-screen clock application, etc).
Both of these options are set in a control panel applet System->Device Lock.
NOTE: I know some people have use memmaid to register the lock application to run on wake up. If you do this, DO NOT select the suspend device option!! This will result in not being able to wake your device up for more than a few seconds (Wake up the device, your notification tells the device to lock, the lock process suspends the device, You wake up the device, rinse, repeat)
If you do this, all is not lost, just soft reset your device and uncheck the option to suspend in the control panel.
Here's a link to the installer (Requires WM5 PocketPC edition):
You will likely need to soft-reset to see the new Control Panel applet.
*NEW* The latest version does NOT require the Lock Device today item to be loaded!