You can pick up an iPhone 4S for dirt cheap and all you will need is the Strava app. You don't even need a cell plan for the phone. If you are only doing 14 miles a day, I wouldn't worry about battery life. If you don't want to have the phone on the handlebar, get a Wahoo RFLKT for $79.00 USD and put it on the handlebar. It will connect to your phone and display data from the Strava app.

If you plan on doing longer rides, battery life will depend on age of the battery if you don't turn on cellular service. Here's a screen shot of a ride from last week. I took it after a member of another forum said there was no way I could do a 50 mile ride and have any battery life left. I have an iPhone 5c that is almost 3 years old with the original battery.