Straight from the Mobile HCI workshop about " Mobile Interaction with the Real World " (see the proceedings), this paper: "A graphic language for touch-based interactions" by Timo Arnall. It actually investigates the visual link between informationand physical things, using cell phone to interact digitally with augmented artifacts and spaces.
Timo's point is not take the counter-approach of existing practices (RFID, NFC...) which "hides" the range of possible interactions with augmented objects. He then proposes an iconography for interaction with objects, based on existing signs.
Sketching revealed five initial directions: circles, wireless, card-based, mobile-based and arrows. The icons range from being generic (abstracted circles or arrows to indicate function) to specific (mobile phones or cards touching tags).
Arrows might be suitable for specific functions or actions in combinations with other illustrative material. Icons with mobile phones or cards might be helpful in situations where basic usability for a wide range of users is required. Although the ‘wireless’ icons are often found in many current card readers, they do not successfully indicate the touch-based interactions inherent in the technology, and may be confused with WiFi or Bluetooth.
The circular icons work at the highest level, and might be most suitable for generic labelling. A simple circle was chosen for further investigation. This circle is surrounded by an ‘aura’ described by a dashed line. This communicates the near-field nature of the technology but also describes a physical object that contains something beyond its physical form. The dashed line distinguishes touch-based interactions from generic wireless interactions.
Why do I blog this? It's been a while that I wanted to post about it and I took this workshop paper as an opportunity to describe what Timo does. I find this work very interesting in the sense that revealing possible interactions to the user is an important point, especially regarding touch (it's not self-revealing for lots of human activities).
Now, thinking about gaming applications, I like what Timo mentions "could be applied to situations as diverse as a gaming sticker offering powerups", there is a lot to think about here: not only for collecting objects/improving capabilities in cities but also dropping game artifacts that could trigger specific behavior to other players (not from your team).