Why don't we have something like Syncthing for APIs?

Syncthing can sync files on devices that are behind NAT using public servers, which is a really useful feature. If we could implement something similar for APIs, it would allow devices to communicate with a common backend without handing data out to third parties.

I think this could be a really useful as it will let users maintain control over their data while still allowing them to use the service. What do you think?