Chicagoans and Bostonians, you have a new way of hailing a cab. It's called "Hailo," and it lets you grab a taxi by app command, rather than an arm raise at the curb. Hailo is coming soon to New York and Washington, D.C., and already is available in Toronto and several European cities. Hailo is different from some other taxi apps in that its relationship is with the individual driver, not with an entire fleet.