Timepieces for the Blind
Generally, there are two main timepieces made for the blind. There are Braille watches which usually have a flip-up cover over a regular analog watch face. By feeling the position of the hands on the watch one may determine the time. The second is the talking watch. A button is pressed whereupon the watch announces the time.
It occurred to me that one could easily make a third type which would instead vibrate a series of pulses that provide the time, perhaps in a more discreet manner than the prior two methods. I knew that I wouldn't be the first to think of it, so I did a search and found only one product which uses this method.
The Vibrating watch, produced by the Royal National Institute of the Blind uses a coin cell battery to keep the time, and two AAA batteries to power the vibrating motor. It's about 3" x 1" x 1.5" in size, and has one large button and two small time setting holes along with a cut-out area over the vibrator. The time is set using a toothpick, bent paperclip, or similar thin rod. A description of how to tell time using it is given in a document on their website. It's available in the US for around $100 from SoundBytes.
The device I had envisioned is much smaller - about 1.3" x 1.3" x 0.25". This is about normal men's watch size. This design would use a rechargable battery that would need to be recharged daily, and would not be user replacable. A more advanced design could easily last a week or a month between charges.
There are certain tradeoffs to each design, and looking further into it I can see that using a regular battery would be advantageous. This causes the size of the watch to go up, but one could readily make such a device about 1/2 the size of the existing solution.
This may become a future project for me just to satisfy my own curiosity. If you would like to see me make a prototype, let me know - if there's a lot of interest I'll make it a priority instead of a curiosity.
Note that while there are many vibrating watches, they usually vibrate for alarms, and do not give time via vibrating. Some braille watches vibrate the hour and minute hands to increase the tactile feel and make reading the time by touch easier.