The HTC HD2, as most devices out there, features a LED which usually notifies you by blinking of any activity such as missed calls, text messages, new email messages and such.

From the creator of KeypadLedControl – which makes the HD2 keypad LED active as long as display backlight is active – comes a new small piece of software that would use the keypad LED to blink and notify for missed calls, text messages and emails. The ZIP file contians two files: onw would check for unread sms and missed calls while the other would also check for any new emails you’ve received. Extract the one of your choice, put it on your device and run it. It will stay active untill a soft reset or until you run it again. To have it automatically start up, place a shortcut for the executable in WindowsStartup.

(Source: XDA Developers)