Good suggestion. I was able to command the car to "lock" four times in a row and I got three taps on the horn. It's not as loud as the solid honks of the alarm, but it's better than nothing. I should be able to honk out "SOS" using the pauses between the honks as the long/short.
Haha... great. I was thinking more for the "find a car in the parking lot" situation you mentioned.