The calipers that were chosen are commonly available, and inexpensive -- under $15 when on sale. They are available at Harbor Freight(US), and Canadian Tire(Canada). They are OEM'ed to large retail distributors, and will look slightly different. So far, from what I've seen, the shape of the electronics housing and the color of the buttons remains consistent.

There are a few people out there who have already interfaced to similar calipers. Some info is available on the web regairdng the different interfaces available.

I needed to be sure about the caliper that I purchase, so, I undertook to have a looksy. Here's what I found;

At first, I thought that it might be outputting in BCD, but that was not the case. Maybe it uses a 4-bit processor?