The invention relates generally to synchronizing functions on handheld devices and more particularly to precisely synchronizing a function among a large number of devices having multiple different platforms. The invention provides the ability to cause a large number of handheld devices to perform certain functions simultaneously, within seconds or fractions of a second of each other. In certain aspects, the invention provides an apparatus for synchronizing a function among devices, including one or more processors in communication with a memory and configured to, for each of the devices, send an event to the device, receive a timepacket, and send a return timepacket, thereby causing the device to receive the event and invoke the function after a delay.