Do it in any language you want to learn. The prize is knowledge!
Some of the more interesting would be Erlang, Elixir, Lua, Rust, Go, Haskell, Ocaml, but also anything more exotic than theese (OTOH an PHP version would be really crazy exotic for this kind of an app).
Connects to gtalk as an xmpp or hangouts (protobufs) client. Connects to my prosody as an xmpp component and forwards messages to my one single account.
Messages to nickname@component go to gtalk Messages from gtalk go to my prosody account
Features in v1:
- single user
- fixed credentials
Features in v2:
- authorization workflow
- multiple users
Features in v3:
- support group chats (muc)
- send/receive multimedia