GPS tech (Garmin, Hammerhead, Wahoo, RWGPS, etc)

So this would give me accurate speed/distance?

http://www.wiggle.co.uk/garmin-edge-500-blue-with-heart-rate-and-cadence/

Also, with the 500, you just get a little black line to follow as a route, don't you? Is it feasible that I could plot a long ride on Bikely, then upload it to that and follow it? Or is it not clear enough to rely on?

I have two options on my Bryton. Little black line, or arrows with distance to turn. The second seems clearer, and uses less space.

Neither are really geared towards navigation though. They are designed primarily to be training aids. With the navigation chucked on, as a brucey bonus.