This looks cool!

However, if the tracker is centralized, doesn't protection against double spends basically come for free?

Or, maybe not because of the other things?

Oh, wait, ok so in this situation does the tracker have any privileged information?

It doesn't look like it, So, another party could take the place of the tracker if the tracker went down?

I don't understand the proof of stake bit in the readme. I don't see anything about staking the coin, and I generally don't understand how proof of stake applies to something like this?