My bike computer is a Garmin Edge 800 — a state of the art unit which, due to the continued presence of snow in the region, continues to collect dust.
I also ride with an iPhone and a terrific cycling app called Cyclemeter. The Cyclemeter app pretty much does everything the Garmin does except the iPhone is a bit too big to clip in on the front of the bike. I keep it in my cycling jersey pocket.
But perhaps I should be taking a closer look at the Raspberry Pi. This video did remind me of my son-in-law.