A T-Probe is a torture/interrogation device used by the Honored Matres against Miles Teg. The device was designed to read the Genetic memory of the subject. It was this device that caused Teg's wild Atreides genes to kick in an allowed him to escape Giedi Prime.
It is described a non-Ixian interrogation device brought by the Honored Matres from The Scattering. The probe builds a 'digital framework' of the person which can be subjected to stimuli, and will respond as the person would. The T-Probe also causes massive, virtually unendurable pain in a living subject.
It is attached to the body through a series of "medusa contacts" placed around the skull and on major nerve centers. An operator can increase or decrease the power supplied to the probe to maximize its efficacy while at the same time not overloading the nervous system of the subject. While being subjected to the probe, Miles Teg's Mentat thinking deduces that not only can it "command his body as though he had no thinking part in his own behavior," but also "The whole spectrum of his senses could be copied into this T-probe and identified ... The machine could trace those out as though it made a duplicate of him."
Shere only prevents the T-Probe from recovering memories directly (as it does for the Ixian Probe) and does not impede any of the other features. Memories can still be guessed at from the model the probe constructs. The T-Probe is what causes Miles Teg's brain to change its structure, giving him the blinding speed and amazing abilities. This mental alteration continues in Teg even after being 'reborn' as a Tleilaxu ghola.