Pocket Watch On Wrist

Help me out here with these watches?

I am trying to find a watch that would be able to slide open. This watch is a watch that can be placed on your wrist. This shows that I am referring to what is similar to "Light" used in "Death Note" which is a Anime. (Watch the last episode if you do not watch). The reason I ask is because I want to be able to answer my house key in the watch. It is not necessary for it to slide open. All he has to do is open. If called a "pocket watch" can you tell me what type it is.

http://www.btbnt.com/watches-c-23.html hope can help u

DWex – Duino Watch for experimenters (Arduino based wrist/pocket watch with LEDs)