It's originated from Indonesia, specifically from Java, if I'm not mistaken. Some of the public Buses are using 3-horn system, thus the "Telolet" sounds come from. And many young children gathers on the sideroad, asking the driver to blow their horn, calling them Om (Uncle/Oyaji etc - how you call an older man there). So "Om Telolet Om" means "Uncle, sound the horn please". It's quite a past time and entertainment for these kids.
Despite this being some kinda joke phenomenon, i think there's a deeper meaning behind it - these kids teaches us, you don't need money or expensive things to be happy, just a simple thing - like the sound of a bus' horn - will do.
