EDIT: the part about "same protocol" is not entirely true: BIP 10 was created for Armory offline, with the intention of supporting OP_EVAL (yeah, long time ago). But it needs to be updated to be more flexible...and hopefully standardized, too. Hopefully, the devs of other applications will be more interested in helping develop it, now that this kind of functionality is closer to actually being usable.
The payment protocol (or a simple extension of it) is intended to be that more-flexible, standardized protocol.
Quote
It doesn't look like anyone else is working on this kind of interface, yet. I guess you can expect Armory to be the first. Should definitely be done within the next 3 months (for linked wallets).
Excellent!