Blueprinting

I have read about the concept of "blueprinting" at the site;
http://trifinite.org/trifinite_stuff_blueprinting.html

I would like to send a different file, via bluebooth, to mobiles 
depending on their manufacture/model/OS etc.  So blueprinting looks 
ideal.  However, when I started to think about what it was doing I came 
to the conclusion that it is very error prone.  I am wondering if I am 
missing some point about how the hash is generated.

Suppose a user downloads and installs a bluetooth aware application that 
registers a service with the SDP database.  Surely now my blueprinting 
hash for this phone will include the service record of the new service 
and hence not match the expected value for the phone type.

Any thoughts welcome as when I mailed a contact related to the site I 
got no response.

Thanks