Am I right in thinking that with a digidash you can program the speedo? what I mean is if I have a digidash do I need a speedo healer on a bike engine? I had one years ago and remembered having to stick magnets on and I think I did away with the speedo healer......

No need for a speedo healer, the DigiDash uses its own speedo sensor with magnets as you say, either on a wheel, prop or drive shaft.