We present GyroPen, a method to reconstruct the
motion path for pen-like interaction from standard built-in
sensors in modern smartphones. The key idea is to reconstruct
a representation of the trajectory of the phone’s corner that is
touching a writing or drawing surface from the measurements
obtained from the phone’s gyroscopes and accelerometers. We
propose to directly use the angular trajectory for this reconstruction,
which removes the necessity for accurate absolute 3D
position estimation, a task that can be difficult using low-cost
accelerometers. We connect GyroPen to a handwriting recognition
system and perform two proof-of-concept experiments
to demonstrate that the reconstruction accuracy of GyroPen is
accurate enough to be a promising approach to text entry. In a
first experiment, the average novice participant (n 10) was able
to write the first word only 37 seconds after the starting to use
GyroPen for the first time. In a second experiment, experienced
users (n 2) were able to write at the speed of 3-4s for one
English word and with a character error rate of 18%.