In this paper we describe our prototyping environment to study concepts for empowering a single user to control robotic multi-agent systems. We investigate and validate these concepts by experiments with a fleet of hovering robots. Specifically, we report on a first experiment in which one robot is equipped with an RGB-D sensor through which the user is enabled to directly interact with a multi-agent system without the need to carry any device. Categories and Subject Descriptors H.5.2 [User Interfaces]: Input devices and strategies, Interaction styles, Prototyping, User-centered design Keywords human multi-robot interaction, heterogeneous multi-agent system, device-free, in situ multi-robot control