The picture is of my ‘proof- of-concept’ infra-red cat monitor, based around a RPi Model A , Pi NoIR camera and motion sensor. As a number of other people have found the IR LEDs are only really good
for a metre or less, but is fine for this application.  At the moment I am driving them continuously from the 5V rail but will change that to switched operation in the next version to make the whole thing as battery friendly as possible. The software is build on some simple Python code adapted from various other projects using the Picamera library.