This code runs on a Raspberry Pi device, with a motion sensor connected to it.

gistfile1.py

import RPi.GPIO as GPIO ##GPIO library
from ubidots import ApiClient ##Ubidots Library
import time ##time library for delays
GPIO.setmode(GPIO.BCM)##set up BCM as numbering system for inputs
GPIO.setup(7,GPIO.IN)##Declaring GPIO7 as input for the sensor

try:
   api=ApiClient("75617caf2933588b7fd0da531155d16035138535")##put your own apikey
   people= api.get_variable("53b9f8ff76254274effbbace")##put your own variable's id
except:
   print "cant connect"##if this happens check your internet conection
while(1):
    presence=GPIO.input(7)#)# saving the value of the sensor
    if(presence==0):##if presence is zero that means the other car is still there :(
        people.save_value({'value':presence})##sending  value to ubidots
        time.sleep(1)##check every 5 seconds if  the other car moves
        print "cero"
    if(presence):
        people.save_value({'value':presence})##the other car left so is empty now :)
        time.sleep(1)
        print "uno"
GPIO.cleanup()##reset the status of the GPIO pins