Markosec:
A single Arduino can handle all that data? RPM pulses are going to be quite fast, plus hall sensor's readings, and even more processing with the display(for now) protocol. If not, using multiple arduinos could be a workaround?
Projecting on a windscreen seems far more feasible than projecting on the inside of a visor, which is what I was originally envisaging.
The data rate you need is not really that high. For example, 6000 RPM is still only 100Hz and your Arduino would typically be running at 16MHz, so you have time to do lots of stuff per crank revolution. Of course, you don't need to refresh the display every revolution, and that would probably make it rather hard to read if the figures were changing at all, you probably only need to update the display values a few times a second.