Play like Chris Thile, in 50 or 60 very difficult steps! Of which these exercises are one...
I don't know where John Moore got these from, or if he created them, but he's the earliest attribution that I've heard for these.
They are similar to exercises that I've seen on Brad Davis' website. They're played very slowly, and must (!) be played with a strict down-up-down-up-down-up pick motion, regardless of which string is being played when.
Indeed, that's the whole point of these exercises. They are to teach your picking hand to find the correct string regardless of what string it was on before and regardless of whether the previous note was an up or down stroke.
They are effective, in my experience. When I do them faithfully, my pick accuracy improves.
Some notes for success:
1)Start at a very slow tempo. Set your metronome to maybe 90 bpm, and play a downstroke on every click (and an upstroke between clicks). Actually, maybe even slower than 90 bpm at first. Maybe 60 bpm.
2)Don't be in a hurry to speed the metronome up. The point of these exercises is to go slow and force yourself to achieve perfection. Perfect tone, perfect accuracy, perfect timing. This burns the correct actions into your muscle memory. Then, when you do play fast, your picking hand does the right things.
That's all I've got. Here's the link.
Wait, that's not all I've got--Mando players: if you want to use these, ignore the top and bottom strings. Or check the mandozine archives, I think they're in there.