Inexpensive infrared digicam

I don't believe it's the same thing, Dave.

The camera you point to appears to merely take advantage of a digicam's intrinsic sensitivity to IR and uses additional IR LEDs for illumination - it records full spectrum + IR. This is fine for close range work at night (as with game cameras) but not a true IR-only camera where the hot mirror is replaced with a cold mirror.

Some of these are referred to as "game cameras", they are normally fastened to trees and have sensors that trip the shutter when game - deer, bears, etc., are nearby. The infrared lights are for night time shots.  I see them listed for sale on local online websites.

How do these cameras work in daylight? I don't see that IR has to be THAT expensive if your camera is reasonably IR compatible. The simple test is to look at your TV remote with the EVF or LCD. I f you can see a bright image of the IR beam coming from the remote then it is worth going further. Next stage is to get an IR filter, preferably one which totally cuts off visible light [ visible to the human eye ]*. You can buy a filter to suit the filter thread of your camera or alternatively you could buy a 6" square or filter gel and share it with three other fellow togs wishing to experiment with IR.
The traps I fell into doing this was to mount my 3"x3" gel in my Cokin holder. The trouble was that with the long exposures light got in through the cracks and caused rings of light/fogging on the image. [Particularly so when the sun was at right angles to camera] It wasn't until I further trimmed my gel down to fit a spare UV filter I had and was able to completely seal off the perimeter of the gel with matt black paint that I started to get consistently good results.
*rather than one which is simply a very dark red filter and is permitting red light to enter the camera to give you a red colored result. True IR filtrate gives a black and white result, though I suspect requires a longer exposure, so requires a tripod or other steady support for the exposure likely 1 second f/4 100ISO in bright sunlight..

A Sigma SD-14 is $599 at Amazon, it's a DSLR that can be used as an IR camera simply be removing the dust filter behind the lens (it was designed to be easily removed and re-attached to the camera without tools by the user).

Here's an example of using the camera in "full spectrum" mode, that is to say with the IR blocking filter removed, but without an IR cut filter on the lens that would let only IR light pass through:

http://www.flickr.com/photos/kigiphoto/4936347464/in/set-72157624704043355/