Ben isn't a huge fan of speedos, and for that reason and because he wants to see what solutions us prototypers come up with, there's no standard speedo or mount for the rotovelo. Yet.
So I've bought a Knog N.E.R.D. wireless speedo and fitted it. The basic problem is that the sensor has to be close to the spokes and also point more or less at the display. With most recumbents this is tricky, but at least with velomobiles it's easy to get the two close together. My problem is that I really want the display on my dashboard, but I can't work out how to get the sensor pointing towards the dash. So I've mounted the display behind a wheel arch. I can see the speedo when I'm riding, but it's not very easy to read. Which is not really a bad thing, it'll still tell me roughly my cruising speed, my max speed and how far I go.