phone number ->XMPP lookups?

There is the easy-discovery version of the "Conversation" XMPP App, and they provide and run a public registry https://github.com/iNPUTmice/QuicksyServer (Apache License)

What would you think about, and where would it fit in, with Chatty or Contacts, to look up phone numbers, to check if they have an XMPP account registered?

Seems to be a simple http lookup.