So here's what I'm thinking:
First, a Ptomaine Detector. Imagine pulling up health inspection data on a restaurant before you took your first bite. The app could correlate reports with ER visits at nearby hospitals and/or link to sales data of indigestion products from Duane Reade. I'm no artist, but the graphic could be a rat with x's for eyes, and a percentage estimate of the likelihood that you're going to get sick if you eat there.
Second, Derelict Radar. If I can track airplane flights on my iPhone, why can't I map trajectories of the homeless in Manhattan? OK, I know this sounds politically incorrect, so what if RFID tags were sewn into the garments of shelter residents to locate and rescue them from dangerous weather? A secondary benefit would be correlating locations with Police incident reports so pedestrians could choose which direction to walk.
Third, a Construction Locator. A unique joy of the NYC experience is discovering that one of those tall orange chimney things bellowing steam from under the pavement just caused you to sit in traffic for a half-hour. Why couldn't that data get fed into a map and made available to cabbies? Ditto for a real-time readout on citywide events, which would let you work around the street closures for the annual Jigsaw Puzzle Appreciation Day parade.
A related fourth idea would be a Babble App that matched business registrations and taxi medallions with applicant countries of origin, and provided basic phrases in the appropriate language. A voice recognition translator would be nice, too.
Finally, why not aggregate weather records with traffic accidents, stock market movements, and any other event-based data sets, and then correlate it with user astrological signs, to produce a Life Quality Meter? Such a readout would be a sort-of biofeedback app, letting users assess their moods, and thereby delivering data about the subject people care about most: themselves.
Do you have more ideas? Let's win this thing!
Jonathan Salem Baskin writes the Dim Bulb blog and is the author of Branding Only Works On Cattle.