Trello is a service that allows teams of people to delineate tasks and assignments. I've used it for various projects, and it's surprisingly effective once you get used to its somewhat unconventional drag-and-drop card/stack system. The design is most effective for large teams that don't often get everyone in the same place. But what about the times when you do happen to be close to your teammates? Enter Google's fancy audio/Bluetooth/Wi-Fi connection API, Nearby, which was integrated into Google Play Services last month.
Now if you want to add another Trello user to a board and said user happens to be near you (and also using an Android phone or tablet), you can do so with the Nearby feature. To activate it, open the menu on the Board view and enable the slider marked "Share Board Nearby." Now any Trello user in the room (so long as he or she is in range of the sub-audible sounds used by the Nearby API) can hop on to the board.
The trick is a bit limited, since once they've joined the board you'll still have to manually add them to individual cards. It seems like the only real application would be a meeting, where it's only slightly easier than inviting someone to a board manually via their standard contact info. The updated app also has a new board search function.