First, from the app description, via the AAWP App Catalogue:
Soundex L320 calculates Soundex codes for surnames for use in genealogy research. Soundex was used to index the 1880, 1900, 1910, and 1920 US Census and can also help identify spelling variations. In addition to the standard Soundex value, an "Ashcraft" rule value will also be provided if relevant. If the surname begins with common prefixes, Soundex codes will also be generated for the surname without the prefix.
So why is this important?
With the Windows Marketplace now passing 40,000 applications, once you get past the big names and web services, it's apps like these that will create the emotional bond in people to their smartphone. The hobby programmer, picking up the tools and just seeing what happens - that's the true strength of a platform, and that's why Easy Soundex is just as important as internet tethering.