We're all familiar, on an intellectual level, that our Bluetooth devices are affected by signal strength. Most of us have even experienced the limitations of Bluetooth signal range when we accidentally walk too far away from a Bluetooth speaker with our phones. But, it's difficult to actually imagine what those signals are actually like, and how they're affected by distance, interference, and obstructions.
To visualize this, maker Toglefritz has come up with a unique and beautiful way to illustrate those Bluetooth signals. The technique pairs an Android app with long exposure photography. Once your phone is paired with the Bluetooth device you want to test the signal of, it will change color as the strength of the signal changes. Taking a long exposure photo (in the dark) while running the app lets you see how the signal changes as you move about the room.
All you'll need to do this is an Android phone, a DSLR (or any camera capable of long exposure), a Bluetooth device to connect to, and a computer with some sort of photo editing software (like Photoshop or GIMP). Once you've taken the long exposure photo, you simply overlay it on a normal (lit) photo of the room, and blend it to produce a kind of map of the Bluetooth signal strength in the room.
The technique is a great way to get a more intuitive understanding of the way Bluetooth signals work. The resulting photos are also just plain cool to look at. A similar technique could be used for measuring any type of signal strength, such as WiFi or cellular.