From their sales flyer:
"T9605 Intro Price $338.80
NEW MAG-ic Probe V4.0 Electronic thickness Gauge This is an advanced and
convenient way to measure the thickness of instrument tops and backs without
disassembling your instrument! Downloadable software lets you record your measurements
directly to your computer on a photo or drawing of your instrument and
map out your graduations! Each MAG-ic Probe utilizes a wired sensing wand (the
probe) that electronically measures the distance to a magnetic ball. As the probe
samples the upper surface of an instrument top or back, the ball follows the sensor
on the inside surface, jumping over braces and tone bars. This provides a continuous
readout of the wood thickness in thousandths of an inch (mils) or millimeters,
accurate to 0.1mm. The effective range of measurement is 0.0" to 0.6" (0-
15mm). Two magnetic ball sizes are included, 3/8" for Violins, Violas, mandolins,
ukuleles and smaller instruments, and 1/2" for guitars or larger instruments."
That's all I know. Haven't tried one.