Originally Posted by Seattle Forrest

People use phones as bike computers because they're cheaper; at the same price I wouldn't go for an inferior solution. A Garmin has a decent battery, if you ride more than a couple hours at a time with the screen on you'll need to buy a separate battery for your phone; a bike computer is waterproof, you'll have to buy a case for your phone if you might ever get caught in the rain, and that will interfere with the touch screen and possibly the battery, a bike computer doesn't have a monthly software charge, etc. Popsicle sticks and bubble gum.