MagPen [8] is a gesture-input technique over 3D space
near a smartphone using a pen to which a magnet is at-
tached. MagGetz [7] is a user-customizable passive control
widgets that realize tangible interaction on and around a
smartphone using magnets and an internal magnetic sen-
sor. MagiSign [9] is a user identification/authorization tech-
nique based on 3D magnetic signatures around a mobile
device that use an internal magnetic sensor. These tech-
niques utilize the 3D space around a smartphone, whereas
our techniques use the surface around the smartphone as
an input surface.