The PinByPin program is the perfect example of something developed based fully on users' requests. It was born as a simple cooling fan controlling program, capable of switching the fans on and off depending on the difference in reading between the external and internal temperature sensors. Then we noticed it could also be used to operate relays, and then the use of PWM (pulse width modulation) was suggested as a mean of also controlling heater bands. It's been used even to control (remotely of course) a green laser pointer, which, coupled to an all-sky camera, is a great tool to reposition the scope in case of problems.
In a nutshell, PinByPin allows us complete control over the output of the 4 power pins of the port in use.