We have grown Fe delta-doped (In, Fe) Sb thin films by low-temperature molecular beam epitaxy for magnetic-field sensors with ultrahigh Hall sensitivity. Magnetic circular dichroism spectroscopy measurements indicate intrinsic ferromagnetism in the Fe delta-doped (In, Fe) Sb layers. Although the Fe delta-doped (In, Fe) Sb thin films have lower Curie temperature than the Fe uniformly-doped (In, Fe) Sb with the same average Fe concentration, their anomalous Hall effect is much stronger. The Hall sensitivity of the Fe d-doped (In1-, Fe-< x>) Sb sample with an average Fe concentration = 17% reaches 1522 Omega/T at room temperature, which is much higher than those of Fe uniformly-doped (In, Fe) Sb, (Ga, Fe) Sb, and commercial InSb Hall sensors.