In 1991, Mark Weiser published his seminal essay “The Computer for the 21st Century” in which he introduced the vision of ubiquitous computing. In this vision, the world is suffused by computing devices which are no longer distinguishable from everyday objects, but blend into their surroundings. In particular, Weiser describes three types of interactive computing devices: wall-sized boards, clipboard-sized pads and inch-sized tabs. Arguably, large parts of this vision have already become reality with the recent “smartphone revolution”, due to which a large percentage of citizens in industrialized countries now carry a close analogue of the tabs and pads from Weiser's original article.However, their usage is hampered by a lack of logical and spatial awareness between peer devices. Although cloud-based solutions may help to address part of the issues related to logical awareness, they exacerbate privacy and security concerns on the other hand. Spatial awareness is currently only provided by centralized tracking systems which preclude use in arbitrary environments. This is particularly evident when regarding aspects such as collaboration with and communication between co-located mobile devices. A seemingly simple task such as transferring an image to another person’s smartphone will leave many average users struggling, in part due to the overwhelming number of options available for this task (Bluetooth, NFC, e-mail, messaging service, …). In the end, most users will likely resort to using a cloud-based service to transfer the image, even though a local connection would be faster and would not compromise the users’ privacy.In this project, we will address these issues by employing peer-to-peer communication technologies and multiple sensors which are available in today’s smartphones to enable ad-hoc logical and spatial interaction between co-located persons, their personal mobile devices, and fixed infrastructure. This allows us to support advanced interaction concepts such as proxemic interaction, mixed reality, or tangible interaction in arbitrary environments without the need for expensive infrastructure or opaque remote services beyond the users’ control. Where applicable, existing local infrastructure such as projection screens will be integrated into the local information space and made available to the users without prior setup.