From Dreams Soft:
So you leave your office and forgot to lock/turn off your PC? Worried that someone would sneak into your private files? Now you have an easy solution! You can use Remote PC Locker and simply send an email from your smart phone (or any device, for that matter) to lock your computer.
The full version of Remote PC Locker supports many more commands other than Locking PC, that includes Shutdown, Restart, LogOff, Hibernate and StandBy.