Ambient Notifier prototype
Ambient Notifier prototype

The Ambient Notifier is a standalone device designed to reduce the frequency of explicit interaction between users and their mobile devices which are due to users wishing to remain updated about the status of their phone.


Mobile phones are becoming an increasingly ubiquitous technology due to their widespread penetration in the public, their growing functionality, and the wide spectrum of activities they support and facilitate.  Despite their mobility, empirical evidence on mobile phone practices shows that only 58% of users keep their phone within arm’s reach, while 20% keep phones a bit farther away but still in the same room. This evidence suggests that users need to periodically interact with their mobile device to check if there was a missed call or SMS. This can be time-consuming, especially since the phone may be in a different room, and can introduce interruptions to users’ activities.

Ambient Notifier

Designing ambient displays is challenging. They need to provide adequate feedforward and feedback such that users can assess what they can do with them, what information the ambient display shows, and how well the display fades into the background.

Ambient displays aim to provide users with relevant information, in the right form, at the time and place it is needed. Another crucial factor in their success is comprehension: how well do users understand the purpose of an ambient display and how to use it.

The Ambient Notifier, uses light to get users’ attention and present information about incoming calls, missed calls, and received SMSs. Publicly exposing the state of a user’s mobile phone is a challenging task, especially since users do not tend to reveal personal information contained in the phone to others. However, previous work has explored mobile phones in the context of ambient displays and publicly revealing information, arguing that interaction with the phone and through the phone reveals and reflects the user’s behavior.


RGB LED attached to Arduino Duemilanove
RGB LED attached to Arduino Duemilanove

The main component of the system is an RGB LED. This is a light emitting diode that can change between red, green, blue and any combination of the three colors. When all three colors are activated the LED turns white.

The LED is connected to an Arduino Duemilanove via a 220 Ohm resistor which was isolated using heat shrinkable tubbing. The Arduino board was extended with a WiShield component to provide internet access, and was attached to a battery for power.  Finally, using a laser cutter an acrylic casing was built to house the electronic components. The LED shines through the acrylic case onto the lamp, thereby making the lamp light up.


To enable the Ambient Notifier to respond to events on the phone, a server was developed to run over the WiShield’s TCP/IP stack on the Arduino board. The server listens for pre-defined messages sent from the mobile phone (or indeed from any internet-capable device):

  • off: idle state.
  • ringing: there is an incoming call.
  • answered: the call was taken.
  • dismiss: cancel the notification.
  • sms: received sms.

A small software service was developed for the Android platform that takes care of detecting different events on the phone and sending the appropriate signals to the Ambient Notifier. The state machine design pattern was used to map the LED’s color to states, and to model the transitions between states.

Ambient Notifier state machine
Ambient Notifier state machine

By default the Ambient Notifier is in the Idle state. When a SMS is received on the user’s phone, the Ambient Notifier changes from Idle to SMS state (blue). An incoming call changes the state to Ringing (green). If the user does not answer the phone, Ambient Notifier changes to Missed call state (red). These states and transitions were informed by the Peripheral Display Toolkit, a toolkit that empowers designers of ambient displays to manage users’ attention.

The toolkit provides support for three aspects of ambient displays: abstraction, notification levels and transitions. Abstraction involves simplifying the information to be displayed, so that it is easy to interpret at a glance. The Ambient Notifier simplifies information by changing phone events into colors. Notification levels refer to differences in information importance, which in the Ambient Notifier map between the no light and light conditions. Transitions are how users’ attention is captured. In the Ambient Notifier, the RGB LED toggles between colors as events occur.

The Ambient Notifier requires a background process to run the users’ mobile phones. A background service was developed for the Android platform, which enables the user to specify the networking address of the Ambient Notifier. In addition, the application indicates to the user whether the phone is actively connected to an Ambient Notifier. This software monitors the phone activity in the background, and detects events of interest. Specifically, the application monitors for incoming calls, missing calls and received SMS.


Three evaluation studies were conducted. Study 1 was a heuristic evaluation adapted for ambient displays from Nielsen’s heuristics. Study 2 was an in-situ informal evaluation carried out with the Ambient Notifier, involving ten users who had the opportunity to interact with the system, see it in action, and provide feedback on its operation. Study 3 was a long-term evaluation involving two participants using the system for 3 weeks. In this study the participants were interviewed both before and after using the system, and the objective was to assess the extent to which the system affected the way users handle and interact with their phone.


The heuristic analysis used to evaluate the Ambient Notifier is an adaptation of Nielsen’s heuristics. From this technique, the following heuristics proved to be useful during evaluation of the system:

  • Useful and relevant information was a focus of the system by displaying phone status to users; 
  • Peripherality of display highlighted the importance of the Ambient Notifier waiting to be engaged and be non intrusive; 
  • Match between design of ambient display and environments was achieved by the Ambient Notifier’s portability and small size, but in its present form is far from being an object fading into the environment; 
  • Sufficient information design indicates that the features level should be kept at an “enough” level, as was the case with the Ambient Notifier; 
  • Consistent and intuitive mapping was achieved by mapping the colors to the events consistently; 
  • Easy transition to more in-depth information was taken into consideration, as the Ambient Notifier triggers the user to use the phone in case they need to know who called, who sent an SMS and what was written; 
  • Visibility of state was achieved since users can perceive that something is going on with their phone. 
  • Aesthetics and Pleasing Design are a useful direction for further improving the Ambient Notifier.

In Study 2 ten users had the opportunity to use the Ambient Notifier and play with it during an afternoon. Their feedback suggests that it was immediately apparent to them what the notifier did and how it worked. This was reinforced by the fact that participants were given a live demonstration of the Ambient Notifier being right next to a mobile phone. This setup made it straight-forward to map events on the mobile phone with the states of the Ambient Notifier, since the two were right next to each other and participants were able to observe both the phone and the Ambient Notifier simultaneously.
Study 3, the longitudinal evaluation of the system with 2 users, revealed a number of insights. Both participants commented that although it was pleasant to have an ambient notion of the events happening on their phone, they found it annoying that they needed to interact with the phone itself in order to “reset” the Ambient Notifier. The participants commented that it would be useful to be able to “shake” or “touch” the Ambient Notifier in order to acknowledge and dismiss the notification.
One of the participants mentioned that the Ambient Notifier was quite helpful to know when the phone rang, especially when the phone was not nearby or the environment was noisy.

“...I like it, it’s like having a lamp that controls my phone activities...”

Finally, the participants commented that the battery life of the Ambient Notifier (1 day) was not sufficient, as they had to recharge the battery every night. A possible improvement on the design of the Ambient Notifier is to enable it to recharge itself by plugging it to a wall socket, much like how mobile phones are recharged. This would avoid the inconvenience of removing the battery before every recharge cycle.

“...I would leave the device near me on the desk, while I had the phone charging... it would light up the desk every time someone was trying to reach me...”