A tangible user interface (TUI) is a user interface in which a person interacts with digital information through the physical environment. Hornecker and Buur state that tangible interaction relies on tangibility and full-body interaction, and gives computational resources and data physical form.

Research, not products
Currently, most tangible interaction concepts are explorations of the possibilities of tangible interaction; design/research projects as presented by the tangible media group at MIT, Joep Frens' Rich Interaction Camera or these students from IDE. So why am I - being a conservative, usability-minded interaction dinosaur - interested in Tangible Interaction? Because I see tangible interaction as a way of making the interaction less conscious, and demanding less resources (attention, effort, time). And as Krug put it: we don't want things to make us think. (It should be mentioned that there are some that disagree with tangibility being a gateway to easier interaction: misconceptions about tangible interaction).

Tangible interaction in a shop near you
So I set out to identify examples of tangible interaction in products that are already among us; that you can actually buy, right now, in a shop near you. They might not be as radical and inspiring as the tangible interaction research/design concepts mentioned previously, but I think that though they are more modest, these are examples of products that really make a difference by providing tangible interaction. (By the way, the numbers are not intended as ranking or something.)

1) PowerMate: a physical volume button for your computer
The PowerMate in essence is the volume button from your teenage stereo set, but now in brushed aluminum, with a blue light beneath it (how cool is that!) and connected to the USB port of your computer, allowing you to quickly and quite exactly adjust the volume in media playing programs. As opposed to clicking that annoying little icon, or hastily accessing your media player if you accidentally play ACDC right after listening to Jewel.

2) Multimedia keyboards: quick and easy control
Several keyboards (Microsoft, Apple) now offer direct access buttons to control the media you are playing. Personally I find it much easier to pause, skip to the next song, or to adjust the volume by quickly hitting a single button, than to browse through my programs and find the right icon.

3) Old-fashioned landline phone: straightforward answering
On (non-wireless) landline phones you simple grab the receiver to enable the connection. About as simple as it can get. In contrast, on (home) DECT phones often you have to push a (green) button to start the conversation, and another (red) one to stop it, which is less intuitive.

4) Clamshells: the motion has meaning
Open up your laptop and it awakes from sleep mode. Seems to make sense: what else would you want a laptop to do besides starting up if you open it? And if you don't want it to start up, simply close it again. Or open your clamshell mobile phone to answer a call. One small complication with the latter situation: there needs to be a display on the outside to be able to see who's calling and decide whether you want to answer the call. And so you also need a way to divert the call without opening (and answering) the phone.

5) SonyEricsson K800i: open lens cover to activate camera
If you slide open the lens cover of the SonyEricsson K800i, the phone switches to camera mode, without you having to dive into menus (and subsequently having to open the lens cover because you don't see anything).

6) Canon copiers: extrapolating what the user wants to do
(Some) Canon copiers do a similar thing: if you put a memory stick in the copier, the device will access the memory stick, assuming the file you want to print is on there. And if you put an A4 document on the glass to copy it, the device assumes you want the paper size to be A4.

7) SonyEricsson phone and iPod Nano: shake to shuffle
Talked about this earlier: shaking your mp3-player to get a random song. Comparable to shaking a box of breath-mints (to get a random breath-mint). Available on the new iPod Nano and the SonyEricsson W910. And on the Sansa Shuffle (next example).

8) Sansa Shaker: tangible group interaction with music
The Sansa Shaker is less of personal music player; with its built-in speakers and physical appearance it seems to be designed to be used in a group. To change a song on the Shaker you snap one of the colored rings (next song) or shake the whole device (shuffle). Adjusting the volume is also done by twisting one of the colored rings. (CNET review on youtube)

9) Guitar Hero and Wii: tangibility in video gaming
A bit obvious maybe, but how much more fun can tangible interaction get? Play virtual sports using the Wii controllers or play the guitar using the Guitar Hero controller, and here the sound change as you raise the neck of the guitar into the air as a living room version of Yngwie Malmsten.

10) Bopit: a truly tangible game
In the case of Bopit the whole game is embodied in the controller. You don't interact through a TV-screen. The Bobit device shouts at you whether you should twist, pull, or do what ever with one of the controls on the product. As you are playing the speed and the complexity of the commands increases. Guaranteed to drive you nuts. Watch this YouTube movie: you need to see this to understand it.

Feel inspired? Feel free to leave your own examples of daily tangible interaction in the comments.

More uselog posts on tangible interaction:
> Tangible interaction: design strategy for usability
> Tangible interaction prototypes at IDE
> MusicCube: a tangible interaction concept for music
> Shake control patent controversy
> Emotional intelligence in design: thesis defense of Stephan Wensveen
> Rich interaction camera: thesis defense of Joep Frens

A big thanks to all my colleagues from the ID StudioLab at IDE for supplying the examples and asking critical questions.
(Top picture: Zygote)