It's an idea that can only be described as brilliantly obvious: create a chocolate formulation of your pharmaceutical.
The original idea, as developed by England-based Lycotec, was to develop a mechanism that could more effectively transport drugs to the liver (and they appear to have produced some intriguing proof-of-concept results in increasing the potency of statins).
However, it's not much of a stretch to believe that patients might be more compliant if their daily medications became noticeably more delicious -- especially in chronic illnesses with few or no symptoms where adherence is considered a problem (such as hypertension).
Of course, if it works there will be safety issues to work through. Child-proofing becomes a much more direct concern, for one. But those issues seem addressable, and the potential benefits could be tremendous.
Sadly, the Lycotec website makes no mention of peanut butter. Let's hope they're on it.