It is unfeasible to establish a trusted-third party in ad-hoc wireless networks. Transferring authentication data under a human user's control and involvement, called Out-Of-Band (OOB) channel, bootstraps device pairing. A number of OOB channels have been proposed. However, none of them is generally accepted due to their lack of adaptability to various devices. In this paper, we introduce a new OOB channel, called MimicGesture, which uses accelerometer-based gesture input. We argue that our OOB channel is suitable for all kinds of mobile devices, including I/O constrained devices, as the accelerometer is small in size and requires low computational overhead. We conducted a usability test in order to check the viability of our channel.