infrared-software
There are lots of ways to process infrared imagery to analyze plant health. Here are a few:
Infragram.org
(more coming soon)
Image Sequencer
(more coming soon)
Photo monitoring plugin
@nedhorning has developed a plugin for ImageJ (aka Fiji, on the Mac) which can do a lot of powerful infrared compositing work, including batch conversion and image alignment.
Python
For those who use the webcam and have a Python interpreter, there are some image processing codes available at Python Webcam Codes.