Here's something that will put you off your omelet. A UK firm called Lifestyle Choices has started selling a fertility test called Plan Ahead which purports to tell women approximately how many eggs they have left in their ovaries. Though it won't provide you with an exact number, it measures 3 different hormones to give you an "assessment."
The problem is, many doctors think this will give women false hope that they can delay their childbearing years, when the rate of egg decline actually varies from woman to woman. The test isn't approved by the U.S. Food and Drug Administration at this time, so if your wife/girlfriend is starting to pressure you for that bundle of joy, you won't have to deal with this kind of data just yet.
Home Test for Biological Clock [technology review]