As I ranted before, there are a lot of chromatic finger workouts around, and to be fair they are probably a bit more intense than this, but I've never really been a fan of chromatic exercises.
Not because I don't think they work though.
If you have 6 hours a day to practice then it makes perfect sense to spend an hour or so on "finger press-ups."
But I, like most people, certainly anyone with a job, don't have 6 hours a day to practice. Whenever I have wanted to focus building finger strength or independence between fingers, I have always tried to do it with an exercise that was also a lick I might actually use in a solo or at least in a diatonic setting.
I have tabbed it out moving up and down the E and B strings, so if you follow the tab, you are giving your whole left hand a work out and practising moving a lick up the neck while staying in one key.
It also help you play around with three note per string patterns using only two notes per string at a time.
It's tabbed in D Minor for no other reason than it's quite easy to move it a full octave on most guitars.
I'd say pick it at first, then progress to using legato.