BIT measures the verticality of a borehole AND of existing piles

Borehole:
BIT uses the auger/bucket itself as the centralizer. Eliminating the need for a heavy-to-move system.
The BIT enables fast and accurate determination of inclination in both dry and wet boreholes.
Large boreholes and diaphragm-walls may be quickly tested several times during drilling to enable real-time corrective action.

Existing piles:
A special centralizer is attached to the BIT sensor and lowered into a standard access tube (No need for an expensive inclinometer tube). The BIT sensor includes a gyro which constantly measures and compensates the rotation of the sensor in the tube.

Background
All piling specifications prescribe the allowable deviation of the pile axis from the vertical.
FHWA rules, for instance, limit the pile inclination to 20 mm/m, or 2%.
The ICE (UK) specifications allow a deviation of not more than 1:75 or 1.33%.

Similarly, these documents also set down the allowable deviation of raked piles.

In diaphragm and secant walls, the specification is typically even more restrictive.