All we need is a start timestamp and access to the current timestamp. If we can improve the accuracy of the 'current' timestamp by hosting it on a remote server

All we need is a start timestamp and access to the current timestamp. If we can improve the accuracy of the 'current' timestamp by hosting it on a remote server, so be it. But I doubt that's necessary. How much do you think the clocks on computers drift between syncs? I would wager if I isolated my laptop and phone from any networks, they'd continue to show the same time for quite a while.