Nice sentiment but relays are servers too.  Except they have no guarantee to store your data, just relay data from one user to another.  Most likely on a relay your data will get nuked.  Servers allow signing, and verification, it's just not all that common.  It would be nice if the phone was the cloud, but generally you want a cloud to be always-on, so phones are not the cloud, at least not today.  I would like the phone to be the cloud, but nobody has said how that can happen, in practice.