That is only 2kHz, even with lots of vanes, you can easily measure this with a microcontroller like an AVR or PIC. The easiest way to proceed is just use an LED and a phototransistor. The transistor drives either an input capture or counter input to the micro, then you can measure the time between pulses to find the frequency of count for a fixed amount of time. Having said that, I dont think I want to be the one holding this gizmo up to a jet engine. You would also have to find some way to make a very sturdy mount.