So I've been playing with Parallax's PING))) sensor on a Prop-2 for couple days. This little thing is flippin' sweet!

For $35 bucks it works amazing as a break beam out to about 8 feet with some sort of wall to bounce off of. Also, I've been playing around with pointing it at an approaching target and triggering events conditionally based on the targets distance.

The sensor seems to have a about a 3' wide FOV, and it's really been amazingly accurate compared to a PIR. I have some test code i cobbled up that flashes a flood at a certain pace when it sees you out 70", then increases the flash as it see's you at 45". It's simple, but a good proof of concept for more advanced applications.

In short:

Dear PIR sensor, blow.