Something closely related I would like to see: a system to identify people ringing apartment doorbells that is visible to tenants. Buildings without video systems or doorpeople rely on "who's there?" as their only means of authentication. Something that could be created and installed cheaply without a major retrofit (so that landlords would actually pay for it) would be great. This device comes close, but seems to be targeted more at homeowners. The device I'm talking would need to be shared among many tenants, and robust enough to deal with drunken buzzer pounders.