Is an implementation already available somewhere?

Happy to hear that it's ok for inclusion in Bitcoin as stated on page 9 of the whitepaper:

"In addition to standing on its own, Sumcoin can be implemented as a sidechain or integrated into the Monero (or Bitcoin) protocol as a hard fork with a new transaction version."

Would be great to have it also implemented in some Proof-of-stake alt-coins like Peercoin.