> 0 to 10 mph

That is very slow. Try to gain access to *both* front wheel's brake drums
and use two proximity sensors near the vent holes in the hubs imho. You
need to OR the pulses in the micro and you need to measure period, not
frequency at that speed.

> laser pointer, 24/24

Only for the 1st 24 hrs unless you derate the current ;). Also temp range
will temporarily weaken the beam very much as it heats up. Beyond 70 deg.
C case most laser pointers are worse than red LEDs. Try to spray freeze on
a working laser pointer some day (not on the lens, it will fog anyway).

Peter