We stumbled across this online and are now wondering if anyone here has seen, or handled the Sig P250 2SUM.
 
This set provides you with a full-size P250, for duty, home defense or sport, and all the components to "rapidly" convert it to the P250 Subcompact, for concealed carry.
 
Basically interchangeable Grips, Slides and Barrels with one serial-numbered frame.  Sounds pretty cool for an MSRP of around $950, since you're basically getting 2 pistols (and Sigs, at that).
 
http://www.sigsauer.com/Products/ShowCatalogProductDetails.aspx?categoryid=54&am p;productid=281