After a couple of weeks (or maybe it was days) of sailing Hérisson I started to look into some kind of Compass and/or Knotmeter. I was just browsing and wasn't necessarily looking for something Electronic.
You will inevitably come across products such as Velocitek's Speed Puck, Pro Start and Shift but I didn't like them at all. Technically speaking they're fine products but they're oddly disjointed to satisfy some "class rules". The Speed Puck is IMHO too expensive for what it is and it lacks a (magnetic) Compass. The Pro Start is a bit better but again lacks a (magnetic) Compass. The Shift has the (magnetic) Compass but lacks the GPS.
I then came across a company called Nova-Sail. There isn't much information about them on the Internet other than people saying they're popular among Dingy sailors in Europe. Coincidentally they had just released the NS360.Pro.
To keep things simple and short: I love it! It has the GPS for measuring speed, the Compass for heading and uses Bluetooth for data synchronization. And a bunch of other features which I'm not using.
Update: As of Firmware 1.8 there's also a NMEA broadcast feature.