In something like BiddingPond, that system could make sense, given that it allows for an automated intermediary to escrow the auction, and I'm sure the people over in gambling would go for it. Currency exchanges could theoretically integrate it, although they probably use RPC.
Ah, right — so it would be more of an RPC interface to the bitcoind than a client-facing site. Yes, I've considered this, and it's a good idea… And if there were 32 hours in the day, I'd be all over implementing it.