the author of this app says:
OnlyMe automatically locks your PalmPilot(TM) device whenever the device is turned off. OnlyMe is quick, easy, and secure.
If you misplace your device, OnlyMe will ensure that no one can read the information on the device. Since OnlyMe locks your device whenever the screen is turned off, you do nothing special to ensure the privacy of your information. Entering your OnlyMe password can be as easy as making one quick gesture with your stylus or finger.