[dragonwriter]

> currently SMS is the only open standard for instant messaging

XMPP is an open standard (through IETF RFCs and related standards) for messaging and presence whose motivating use case was instant messaging: http://en.wikipedia.org/wiki/XMPP

[imissmyjuno]

Right. My comment is more on the adoption rather than availability of open standards.

[pjscott]

XMPP is also used, behind the scenes, with Google Chat and Facebook Chat. It has a fair amount of adoption; you just don't really hear about it much.