With the failure of my Strava app last week, I decided to get a Garmin device. I was very generously bought one as a belated birthday present. I went with the Garmin Edge 25. It’s about the size of a 50 pence piece and attaches to the stem of your bike. The advantage of the 25 over the 20 is that it comes with Bluetooth, so can get it to sync with your phone rather than having to plug it into your usb port with the cable.
Having signed up for the Tour de Bristol in April, I haven't done any training yet and the countdown is now at 34 days.