Need IR sensor that will detect a cat

I'm not looking for a motion detector, I'm looking for a directional sensor that I can mount on a servo that will let me "look" for a hot body. I want to know where it is so I can follow it. I know how to get the distance once I have a 'bot pointed at it, but I need to figure out which direction it is in.

Just wondering if anyone had found a sensor that worked for that purpose. I realize the detectors are probably not very directional so I thought about sticking it in the end of a tube to prevent side radiation from being detected. Even if there is some leakage, swinging it back and forth to get the highest magnitude would get me there.

Anyone had success with a similar project and would share a part number?

Thanks, Jim.

If I needed to do this I would not use an Arduino but a Raspberry Pi running OpenCV and this camera :- http://www.cnet.com/news/heat-seaker-thermal-imaging-camera-for-the-masses/

Grumpy_Mike: If I needed to do this I would not use an Arduino but a Raspberry Pi running OpenCV and this camera :- http://www.cnet.com/news/heat-seaker-thermal-imaging-camera-for-the-masses/

I've toyed with that one, but the current platform is a bit too small to house a Pi and enough power. I've done some openCV programming with the Pi and it's pretty good. Not horribly fast but workable. If I can't find a satisfactory IR sensor, I'll put a stationary Pi and camera in the room and communicate with the Arduino via an RF link.

Thanks, Jim.