Have you heard of Agendia?
It is the first company to receive FDA approval for an array based diagnostic screen. The assay is designed to measure the expression level of 70 genes, which have shown an association with the aggressiveness of Breast Cancer. The tool is designed to the aggressiveness of a tumor and could help to design more appropriate i.e. personally tailored treatment programs.
This is one of the fruits of the human genome project and there will be more to come. They won't all be great tests, there are concerns the Agendia test errs toward identifying tumors as more aggressive than they may be.
Unregulated 'tests' like this are already in use. The FDA has expressed concern and is looking to being to regulate their approval (honestly, I think this is a good thing). An industry consortium group thinks otherwise: http://www.genomeweb.com/issues/news/138379-1.html (reg required). They are concerned that high hurdles to approval will stifle development and innovation - I don't agree.
It's going to an interesting next 20 years in medicine, I'm looking forward to watching it play out.