Kury boss is obviously the cheapest solution IF you already have/want the kury grips. I've got one and it makes long distance rides more comfortable. However you still can't remove your hand from the grip.
A real cruise control's obviously the BEST solution, but it's expensive and can be a pain to fit.
Throttle locks are a happy medium. The
Vista Cruise is probably the best bang for buck, but if you can afford it the
Brakeaway is a superior product with better features.
Of course there's a lot of members here who just use a rubber band jammed between the grip & switch box.
