Endomondo is a free app for Android keeps track of workouts. I use it mainly for walking and bike riding but there are many different categories from indoor biking & treadmill to sports like surfing and tennis. You can join challenges, create a training plan follow routes and make friends! It keeps a history of all activities so you can review them quickly.
I have found this to be very accurate and it keeps me motivated by telling me my average pace per mile (you can also turn this feature off).