How do i build a laser based tachometer?
A laser could be useful for this since you can easily create a well placed small dot from the 1 m away.  Laser light is just that, light.  Any phototransistor or photodiode that is sensitive to the laser light wavelength will work.  You might need some optics to gather the reflected light from a larger area and then focus is onto the receiver.  That will greatly increase the signal to noise ratio, but will need to be aligned carefully.