The folks at TEC Lingo (great name?) are claiming title to the “worlds smallest mouse”. The mouse measures in at 27.5 x 60 x 19 mm and weights 0.8 ounces.
“800 dpi, 2.4GHz with a range of up to 32.8 feet, and about 15 hours battery life with automatic shutoff if left dormant for five minutes. No indication of stateside release, but if you find somewhere to import it, at least shipping won’t be too terrible, all things considered.”