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4 bit counter
You can track wheel rotation directly with an optical sensor, as long as your speed does not overrun the roughly 40 HZ poll rate of the PBASIC stamp. We have done this, putting reflective tape on the shaft that drives a chain to the wheels, making it half reflective and half black, and tracking the on/off and off/on transitions. You can track moderate speeds with no counters at all, counting into a variable in the program.
Wanting to track with high precision at high speed, we are trying 4 bit counters using the "7394" chip, a 4 bit binary counter. A viable digikey part is the low power shottky version, SN73LS94N on page 348 of the pdf catalog. The part is easy to use, and you could quickly put it together with a "solder breadboard." Students on our team did artwork for a PC card, and exposed and etched printed circuit boards for the counter. Your program, in this case, must invert the bits, and detect and handle overflow. You should be able to measure inches, or less, at full speed, using this part.
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