Just get a bike computer, it will do distance, time, average speed just like your phone, and it will even do more, like cadence! Plus if it does auto-start, it's actually more accurate with starts and stops than hitting up your watch every time you're at a stop light. I just got a cannondale IQ114 this week from AWWYEAH bikes online for $15! Well I had to buy a new battery, so $20, but still . . . once I got it installed and calibrated correctly, it was within .04 miles of my google maps estimate over 5 miles, which is easily as/more accurate than my gps on my phone, especially because on long rides more than 10 miles I hop cell towers several times and lose fidelity/accuracy. Plus it's super fun and motivating to look down at your computer every once in a while and keep yourself going, instead of waiting for breaks to look at your phone and find out you were actually really slow even though it "felt" hard. Unless of course you're the type to put a huge mount for your iPad on your stem so you can get real time updates from facebook while you pretend to work out.