Quantified crowd, a vision in which on-body sensors of nearby people collaborate to detect various phenomena within a crowd and produce feedback, is an emerging research area. One of the issues that impedes progress in this new area is a lack of a broadly applicable experimental platform, such as the platforms that enabled research on wireless sensor networks. In this paper, we aim to address this issue by presenting such an experimental hardware-software platform. Not only does the platform introduce custom badge-form low-power devices that feature a number of sensors relevant to quantified crowd, but it also ensures that these devices can interoperate with commercial off-the-shelf smartphones, wristbands, and other devices for self-quantification. In effect, it constitutes a powerful experimental instrument, as we show in a preliminary real-world evaluation.