On the upper east side, and in many other parts of the city with big apartment buildings there are taxi lights on the corners, and lights on the awnings of buildings.  Residents can call down to their doormen and the doorman will turn on the light.  Passing cabs on the avenues see the light and make the turn looking for the awning with the yellow light on.

Wouldn't it be wonderful if we could similarly call a number, a taxi light on the corner of Grand and FDR and a light further up the FDR would also go on.  Free taxis heading southbound on the drive, or getting of the drive to drop off a passenger would see the taxi light and then look for the building with the light on.