It's here! I was thinking of a GPS for my sport activities long time ago (around 2006 I bought a book about GPS) but now Garmin sells the Edge 705.
The Garmin Edge 605 and 705 are GPS with sensors dedicated to bikes (street- and mountain-bikes) and this latest generation can display maps too.

Using GPS to record training data and having a map that shows your course is somewhat different to a GPS in your car. I still have to learn a lot.