An electronic signature where, how and when you want it.
You will be able to associate a single cryptographic identity with a set of private keys (which have been saved, are always verifiable and transparent) on a blockchain, i.e. a trusted third party.
So it is as if a document signed with SignChain had been signed before a virtual notary who guarantees its integrity, unalterability and provability that it certainly existed on the date it was signed.