Senseg patented solution creates a sophisticated sensation of touch using Coloumb’s force, the principle of attraction between electrical charges. By passing an ultra-low electrical current into the insulated electrode, Senseg’s Tixel™, the proprietary charge driver can create a small attractive force to finger skin. By modulating this attractive force a variety of sensations can be generated, from textured surfaces and edges to vibrations and more.
Unlike effects created by mechanical vibration and piezo solutions, Senseg is silent. With Senseg application developers have precise control of the location and type of effect users experience. What’s more, Senseg technology scales from touch pads, smart phones and tablets to the largest touch screens without increasing manufacturing complexity.
http://senseg.com/technology/senseg-technology
I wonder if it would be possible to use something like this to create a range of different haptic feedback experiences to a ring/wrist-band wearer. Several different types of discrete alarm?
I imagine the power requirements are too large, but it's interesting.
//Mik