See what competition there is. Then see if I can code it. Then
grok the problem domain through and through. Then start coding it myself without telling anyone. (Then quickly lose interested because the challenge has been
solved and there is only gruntwork left ... But that's
me ![Razz :P](./images/smilies/icon_razz.gif)
)
But of course, if we are talking about a
mobile app and not a desktop app, I would do it only if its utility would outweigh the amount of addiction and/or distraction it would cause. Then make sure that it can detect and block use when used in a moving vehicle.