Before you go out to look for a wonderful technology solution to track all your influencer, chart their progress and measure their input (good luck!), first think about some basics:
1. Find out what will you not be able to measure?
Understand what is beyond your reach, what is hypothesis and when you're throwing good money after bad.
2. Have an idea of what success looks like
This is not to say you try to come up with the answers before you have asked the question, but know what is a good or a bad result (hint: you don't have to sent these too high initially, especially if you're sure you can surpass them)
3. Measure everything
Failing to set an initial benchmark can be fatal. Measure before you start, after something happens and then again as frequently as you can.
If you are looking for ways to measure your traditional PR, then http://www.consulttheguru.com/marketing_ideas/public_relations/measure_value_pr.aspx is usually a good place to start.