Ok, I had to make a decision. Since the intent is to make a simple people tracker, I opted for the most basic sensor available....the IR sensor. Here is a photo of the most basic sensor possible. The transmitting LED is not included because it does not have to be part of the same circuit. No Op Amp either, I will decide later if I want to amplify it or not.
There you have it, 3 connections, Ground, Signal, and Vin (5v)
If you haven't noticed, the phototransistor in the photo is backwards...so, don't do it like this ;)