On Dec 13, 2012 the City of New York's Taxi commission voted to allow electronic hailing of taxis.
UberTAXI launched in September 2012 but was shut down a few weeks later by taxi officials due to a rule that forbids prearranged rides in taxis in New York. That rule is somewhat unique to New York, in other cities where cabs are rare most rides are prearranged (by calling a cab). In New York, calling a cab to pick you up is illegal. This makes it difficult to get cabs in less busy parts of new york.
The recent approval will allow a one-year pilot program to allow companies to prearrange cab rides. This means that uberTAXI (already live in New York) and other companies like Flywheel can now operate in the largest taxi market in the US.
Uber operates in over 20 cities and 3 continents and uberTAXI is live in San Francisco.
Uber provides a great service, and adding taxis to their array of transportation options (black car, hybrid, SUV) is a great additional transportation choice.