I'm working on this project that will be used for reviewers to test PC case fans. It will work with both 3-wire and 4-wire (PWM) fans. It will read and display RPM, PWM % (if it's a PWM fan) and fan voltage. Control will be a trim pot for the PWM and another for the voltage. It will test in auto mode and find the fan start value (PWM or voltage) and max RPM. It will also be user-selectable for certain PWM or voltage values (via the trim pots) so a user can set the fan to say 7V or 50% PWM and take noise readings with a sound level meter.
This project is partially working but still needs a lot of further development and testing.