If you were looking for a killer app, here are some things that could be done with a framework like this:

DDNS
Corporate registry
OTC corporate shares exchange (subchain of corp chain)
Voter registry
Land registry
Corporate Bonds/Debt (repayment unenforceble?)
Local voting (out of the box independant and verifiable etc.)
Payment Reciepts (?)
Insurance (?)

Thats what comes to mind, any other ideas?