Cycling GPS Sat Nav Systems has some cyclists satnavs.
You can buy maps for them or just copy waypoints, tracks and routes from sites.
There are specific satnavs for motorbikes that are waterproof etc. But they cost a lot and expect to use power from the battery. I do not think there are satnavs like that for bikes.
What I have used in the past are 2 possibilities:
1. Use a car-satnav set it to pedestrian and pick the routes you like best and let the satnav recalculate. It is easy and cheap and works well. I have a Garmin Nuvi with European maps. Means that you will always find the campsite back. Handy if you did not plan anything and just go for a short trip for fun.
2. Use a GPS for cyclists like above. I would use oziexplorer to select the routes and then upload the points and routes into the GPS and fit the GPS in a clamp on the bike. The advantage is that you will follow exactly the path stipulated in the books and it does give very good indications of where you are, how far it is etc. For longer journeys a GPS will keep out the moist, run 1 or several days on AA or AAA batteries and allow you to later import the logs/tracks so you see exactly where you've been etc. I would also upload some touristy info (campsites, bike-repair-shops, other lodgings etc.) if they are not already in the GPS.
For a trip like rustic's I would not use a car-satnav but a weatherproof one that runs on AA or AAA batteries because they are more practical. In his case I would download the coordinates of the trip as mentioned in the books etc. and some other info. While riding the bike the occasional glance would tell me whether I was on the right track and where to go.
The North-Sea coast route has a lot of paths through the Dunes and nature areas.
The additional information I would just look up on google-maps (some searches and saving points to a private map on Google-maps then download as KML and convert to a format for your GPS (with GPSBabel)).
This is just the way I do it. I have found it takes the stress out of cycling abroad. You always know exactly where your are and exactly where you need to go & how far away that is.
