I worked for many years at nTAG Interactive, a startup that made interactive nametags for conferences and meetings. We created a device and a web system that allowed organizers to adjust their event in realtime to meet the needs of their attendees. At registration, each attendee was given the wearable pda-like device, which had a small screen with a menu-driven interface showing their personal agenda, session surveys, people they met, and some fun games.
Being an early member of the team, I worked on all parts of the system. I wrote the first web system, then worked on the second generation portable device. I also rewrote parts of the custom 802.15.4-based radios, and spent a lot of time on application development and product specification.
nTAG very suddenly went out of business.