Is there a good way of assessing an estimated absolute value of a currency? If we want to figure out the strength of a currency relative to another currency, we look at the exchange rate between the two. However, I'm wondering what is the most accurate way of assessing the absolute value of a currency?

I suppose commodities or gold could be used, but there can be variations on the value of those over time (i.e if there is a new use for gold in electronics, the value is obviously going up.) So have economists found a better way?
Actually there is an effort by IMF that indirectly offers a common unit of measurement to express the value of the major world currencies homogeneously. 

It's called SDR (Special Drawing Rights) sometimes abbreviated as XDR. It's a sort of meta-currency whose value is calculated as follows:


  The value of the SDR in terms of the U.S. dollar is determined daily
  and posted on the IMF’s website. It is calculated as the sum of
  specific amounts of each basket currency valued in U.S. dollars, on
  the basis of exchange rates quoted at noon each day in the London
  market.
  
  The basket composition is reviewed every five years by the Executive
  Board, or earlier if the IMF finds changed circumstances warrant an
  earlier review, to ensure that it reflects the relative importance of
  currencies in the world’s trading and financial systems IMF website