If you feel the need for a bike computer, these get good write-ups.
Cheapest I've ever seen them.
Garmin Edge 810
Quarter-turn Bike mount
Sleek, lightweight GPS-enabled bike computer with 2.6" colour touchscreen and simple user interfaceTracks details of your ride including speed, distance, time, location, elevation and personal records
Connected features include live tracking, instant uploads, social network sharing and weather updatesInstantly upload ride data via the Garmin Connect™ app on your mobile
Activity profiles allow data fields and settings to be configured to the type of riding you doBuilt-in basemap and optional detailed maps for navigationCompatible with ANT+™ heart rate, speed/cadence and power sensors