Force Sensing Resistors in sidewalks

What about sound? Install a linear array of equally spaced microphones or geophones (the more the better) at the inner edge of the sidewalk. Sample the microphone signals with a common clock. Depending on the location the sound of the step will need different time to arrive at each microphone, and from these differences, the distance between two microphones, and the speed of sound in the sidewalk material you can obtain the position.

Mit freundlichen Grüßen

Frank-Christian Krügel

Don't try to reinvent the wheel:

On a piece of hot concrete?

A TV camera and motion sensing circuitry or software.

try using IR (infra red).

It'd work better. those sensors aren't triggered by heat, they're triggered by changes in heat. they detect motion.

A specific person or just a person in general? One on his own or in a crowd?

Why not set up a web cam with motion detection software?

Yes, they track motion by changes in heat patterns which can be masked by a hot background radiating a lot of infrared. Being 100% disabled, I have quite a few IR motion sensors around here to turn lights on and off. On really hot days they don't work at all. I've also had problems with IR detectors on cold days where minor air current would constantly set them off on burglar alarm systems in cold northern states.