What is the difference between a 1-Way and a 2-Way remote start system?

The easiest way to describe a 1-way system is that it functions the same as a factory remote but with much greater range. When you press a button the remote starter will execute the command and the vehicle will respond with parking light flashes. A 2-way system does the same but it also sends a signal back to the remote to notify you that the command has been executed. Notification is done by LEDs and a series of audible beeps on a 2-way LED system or by the LCD screen and audible beeps on a 2-way LCD system. 2-way systems generally have a greater range and are typically more desirable since you do not have to be within eyesight of the vehicle to know that the command has been executed.