A user can initiate the transmission of data on a mobile device by making physical contact with another device. The physical contact can be any type of physical touch that is referred to as a ‘tap’ or ‘tapping.’ When a tap is detected by a device, the device may initiate near field communication (NFC) with the other tapping device. NFC may be used to communicate data between the two devices, or NFC may be used to exchange sufficient information to allow the devices to establish a communication channel via another communication link. In some embodiments, an NFC-enabled mobile device can be used to gather group data relating to users having mobile devices that are within NFC range of one another and which initiate the aggregation of group data by the tapping of three or more devices.