Time, and software has moved on. With the quality of digital imaging now available, and with the advent of packages with a good "Trace" function capable of generating vector outlines from bit-mapped images, the time of "digitising tablets" for accurate generation of technical drawings is well past it's sell-by date.
Starting with a scanned image or photograph I use Photoshop for bit mapped image sizing, manipulation and processing then Illustrator for vinyl cutting vector art generation or Bob-Art for machining jobs.
The only potential problem when photographing parts is distortion of the image caused by short focal length lenses, and/or having the focal plane too close to the object, by using at least a 50mm lens with the focal plane at least 1m away for parts up to 100mm length the results are good. For larger parts hanging on a wall and using a telephoto lens from longer distance would make sense.

- Nick