As we all know at the moment Bitcoin is not quite ready to be a payment system for everyday use. Many people put their efforts towards that direction (including myself) but it didn't work that well. Bitcoin still remains merely investment and speculation tool.
I analysed what could be the main obstacle in this process for Bitcoin. My conclusion appeared that exchange rate to local currency is the main problem here. There is no fully "trusted" source of the rate. We do have rates from the leading stock exchanges, we do have average or weighted aggregates of those rates. But still that sources are "points of weakness" in the system. We can't trust them that way like we trust blockchain information.
Therefore I came out with an idea to add to the blocks exchange rate information. Not necessary for all available currencies, world reserve currencies would be enough (USD, EUR, GBP). A peer will collect exchange rate from any available source or sources (or establish its own). Then miners averages and confirm such rate in the block (dropping obviously rubbish values). It becomes an "official" rate like Central Bank's rate in each country. Though commercial entities are free to add their own margins as commercial banks do now.
It should not be integral part of the Bitcoin protocol but kind plugin functionality. We can drop it when turn the world to Bitcoin economy.

Pleas give your thought on the idea and its technical implementation possibility.