Today on the Watchismo blog, a tremendous pictorial history of kids' watches. I love this whacky Sears HAPPYTIME watch!
See also:
History of armored military watches
History of slide-rule wristwatches
Early days of plastic watches
Mechanical "LED watch" from 1970
History of calculator watches
Steampunk watch
Belt-drive watch
Watch guts of great beauty
All-plastic watch movement from the 70s
Awesome, impractical, expensive watch