Hello there,
Thanks for posting on our community forums! From what I currently see, we do not offer signature on international shipments using UPS One Balance. However, I know we're rolling out more functionality on a weekly basis, I just haven't heard of this feature in the immediate pipeline.
For direct delivery to UPS shipments, I don't see that we have that functionality available for UPS but I'm happy to submit a feature request for our developers to look into adding that functionality.
I hope this helps!