It is not possible, because the electromagnetic waves emitted by the alarms are encoded in very low frequencies (+ - 430Mhz) in relation to a smartphone, it would not be possible to reproduce this type of wave through a cellular device without specific hardware to emit and properly encode this wave.
Detail: If a determined criminal really wants to get into your car, you can use a code grabber to make a copy of your "key." A code grabber is a radio receiver sensitive to your transmitter's signal. He receives the code and registers it. If the thief intercepts your "code to deactivate," you can program another transmitter to mimic your unique and personal signal exactly. With this key copied, the thief can "fool" your alarm system the next time you leave the car alone.
To solve this problem, advanced alarm systems establish a new set of codes each time you activate the alarm. Using rotary code algorithms, the receiver encrypts the new deactivation code and sends it to the transmitter. Since the transmitter only uses the code once, any information intercepted has no value.
Unless you can figure out how to use this rotary code algorithm, you can not reproduce the emitted signal.
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