The extra batteries for the flashlight 'came in handy' [=were useful] when the electricity went off.
He always liked to keep a dictionary 'handy'. [='on hand, nearby']
('Brit') My flat is 'handy for' [=near to] the underground.
(..) See? No. Someone in Sichuan Province, China... ...is using his computer to turn our lights on and off. Huh. Well, that's handy. Um, here's a question. Why? Because we can. Oh! They found the remote-control cars. - But wait, wait, what's on top of them? - Wireless webcams. Wave hello. (..)2008 TvShow: The Big Bang Theory Title: The Cooper-Hofstadter Polarization Season: 1 Episode 9