(I originally made this suggestion in the Developer's forum a long time ago.)
Being able to place gnomes and train them to say things is nice, but gnomes could be a lot more. I think that the API should allow them to become a portal into the world; able to receive nearby events and generate simple actions as a result.
I propose that gnomes placed on home streets would a message when a player enters or leaves the street, as well as when they approach or leave and when they interact with the gnome.
This would allow many things, such the ability to use a gnome as a nanny-cam on your home street by logging who arrives and leaves. Anyone want their own secret agent 003½?
Other more interesting applications would allow people to script their own interactions with other players through the gnomes and the API. There could be some new verbs on gnomes to generate hooks or the verbs could even be custom. Then, each time a player interacts with the gnome, the API would route the message to registered handler to allow a custom response (text, emote, etc).
This represents a different pattern than that currently available in the API, but I'm confident that it could be designed in a way that wouldn't put too much load on the Tiny Spec servers if we thought through the use (and failure) cases.