Seatsurfing can be self-hosted for room and desk booking — and it solves the "who is sitting where" problem. What it did not solve is the physical side. Once people stopped sitting in fixed offices I kept walking into the wrong room looking for a colleague. The booking system knew where they were. The door did not.

I could not find a door sign to buy that ran on batteries without a licence, a hub, or a vendor cloud, so I built one. It is an e-paper display that wakes on a schedule, queries the Seatsurfing API directly over the LAN, draws who has the room, and switches itself off again. Tap it with a phone and it books the room on the spot; the NFC tap alone powers the chip that wakes the rest, so it works with the device completely off. That part picked up an honourable mention in the "Least Power" category of Hackaday's Green-Powered Challenge last year.

It does not deep-sleep between updates — a MOSFET disconnects the whole circuit from the battery and a real-time clock switches it back on, so in between there is no microcontroller running at all. The oldest unit has been on a wall for 15 months on one set of three AAA alkaline cells and is still going.

I already included a few more uses for the device - including home assistant and homematic. I am very much interested in more ideas!

Firmware, PCB and 3D-printable case are open source.

Hackaday project and logs

To find out whether there is enough interest, there is a pre-launch page on Crowd Supply.