It does not turn the TP "off" just the radios.
http://www.infinityball.com/autoonoff
Auto On/Off V1.0
This is a simple Windows Mobile Professional application that will turn the Cellular and Wifi radios on and off at a predetermined time every day. This will allow you to prevent calls while sleep, thus greatly extending the battery life. Of you could setup the phone to only sync your data via Wifi while you're asleep, which saves on data and battery life. This application will replace RadioOff, which was originally designed for Windows Mobile Smartphone devices (works on PPC as well)...if you're using a device that running WinMo Standard or don't have a need for the Wifi/Bluetooth radio control, then use RadioOff.
This application is in its early development stages and may be buggy.