The first thing you notice about Hosain Rahman, CEO of the much-buzzed-about gadget maker Jawbone, are his wrists. A big, hirsute, 38-year-old bear of a man, the Jawbone CEO has forearms that are a colorful study in self-expression. Both wrists sport multihued, braided bracelets, gifts from his small children. Below his left hand Rahman wears a massive gunmetal International Watch Co. timepiece, which he sheepishly acknowledges gives off a flashy, rich-guy vibe. On his right wrist is a gray UP3 fitness-tracker bracelet, his company’s latest offering