I keep a computer on because I like to know whether I should applaud or berate myself after rides. I currently use a Cateye cordless and I like it so far. Not cheap at $40 but I've tracked my mileage for several years and like to see what works and what doesn't. When locking up I just throw it in my pocket unless I'm using my old beater which has a computer that zeroes real easy if put in a pocket. I just leave that one on the bike.