(Thanks for highlighting Dark Sky, that looks like an interesting app!) Don't your arguments (and app recommendations) point against a UV measure as being usef

(Thanks for highlighting Dark Sky, that looks like an interesting app!) Don't your arguments (and app recommendations) point against a UV measure as being useful? If you want to know whether or not to put on sunscreen now, for a day out, knowing the current UV strength is no use since the conditions will be different later. That's where weather prediction comes in and makes your one little watchband UV datapoint useless. Looking up at the sky and observing weather conditions will always be better than that, and better weather prediction will beat looking up at the sky.