The brief
The idea, for Coca-Cola, was a vending machine in the shape of a Coke can that would read a visitor's brainwaves, turn the reading into a piece of artwork and email it to them there and then. It was an unusual thing to ask of a vending machine, and there was no obvious place to start.
What I worked out and built
I wrote the whole software side. The machine ran a Unity application on its interactive screen, with a hosted Node server behind it. Visitors wore a Muse headset (an off-the-shelf consumer EEG headset), and the software read their brainwave data, generated an artwork from it and sent it to their inbox.
The real problem was the signal. A consumer EEG headset on a stranger, in a busy public space, gives a noisy read, so I built the system on the assumption that plenty of reads would be poor. When the signal was bad, fallback handling and baseline randomisers took over and the visitor still got a proper piece of artwork. That was settled before the machine went anywhere near the public.
Constraints
The machine stood in a public place and was used by one stranger after another. A brand ambassador was on the stand to help people with the headset, but nobody there could step in on the software, and I wasn't on site myself. It had to work for the full length of the activation on that basis.
The activation ran in Covent Garden, London.
Outcome
Nothing went wrong in the field. The software ran for the whole activation without me there.