There's a rather interesting device on display in my college - it's a keypad that was part of a system to assist blind people use DOS made by IBM for the PS/2. As far as I can see, it looks like a Model M numpad with extra large lettering and a different layout. It has an SDL connector on the back, and from what I read, it connects to the PS/2
mouse port. There's info
here and more info with a low-res pic
here. I have a pic of my own which I'll post up once I get the cable for my phone.