SMS alerts
My credit card ie Citibank provides several credit card alerts, one of them is sending an alert when the amount charged is above Rs 5000/-. It does work, last time we had bought a sari, my card is swiped and when we reach home my phone beeps me saying XYZ shop has charged x amount. Now they are getting to me really fast. So couple of weeks back we had bought a bunch of saris. I swiped and by the time the machine printed out the acknowledgement my phone beeped saying the amount had been charged.