No.
It is only possible to measure fitness for a specific task. Often a trait that would help in one situation will hinder in another.
There are two things you need to measure, ability and determination, the first you can test for the second can only really be shown by a track record.
Ability is very task specific, so what you test for will need to depend on what sort of potential you're looking for. For example for programming a number of studies have shown one of the strongest indicator of being able to program is the ability to form a consistent mental model of how something works (which you can test for without someone having programming experience).
WARNING, in some jurisdictions IQ testing is of questionable legality within a job setting and can be considered discriminatory (I know, stupid. They now say you can't discriminate between candidates based on intelligence.)
Highly recommended reading, both as entertainment and as preparation for the inevitable.
I think a better question would be "How do I help people live up to the potential they do have?"