This will log all incoming and outgoing calls and publish them as private appointments on your calendar.
This is great for logging when you talked to someone, or you can just go back and edit the new appointment and add notes directly to it.
After you install it you must either launch it manually by browsing to the installed file location, or you may simply reboot your device and it will launch upon the next boot automatically.
Requirements: Windows Mobile 5 or greater .Net Compact Framework 2