I use Ultrablock 30+, it's good for 6 hours. It was recommended by a friend who is a fast bowler in cricket. He applies it doesn't have to wipe his palms dry, picks up a cricket ball and bowls, no residue. The word been used now is "Colipa" compliant, this product is. Sweat can shorten the duration so the water resistant cream is excellent for midday rides.
Reasonably accurate, I use it when riding in our nature reserve, again it depends on the device used. I use an iPhone, the ride starts with a substantial 3 km climb with many steep climbs and descents in between start and finish. I end at the same spot and always have a variance of about 15 to 20m, thats after climbing about 600m, I think thats pretty good.
