$20 Fisheye digital imaging

HG writes – “The concept of a low-cost fisheye digital camera is very appealing. Unfortunately, fisheye lenses still carry the price premiums associated with limited market “specialty” item status. This paper describes how a commodity door peephole can be used as a fisheye converter lens, thus bringing the total parts cost of a serviceable digital camera with a fisheye lens to under $20 US.” [via] – Link.